Ball joint aren't too awful to replace. The main issue is that you have to remove so many pieces to replace the ball joints that you probably should assess everything else while you're into it. Ever hear the phrase "In for a penny, in for a pound"... If you need to replace any other parts, such as axle shaft U-joints, differential bearings and seals, spindle seals; then now would be the ideal time to do it.
Since you're going to be fairly deep into pulling the front end apart, do you know the condition of the differential bearings, ring/pinion and seals? As you'd need to have all the same stuff apart to do the ball joints, it might be a time/money saver to R/R the differential (if necessary). Are you planning on replacing the tie rod and drag link? What condition are the leaf spring and stabilizer bar bushings?
Think you could give me a list of parts and tools needed? I want to make sure I grab all the right stuff before I start a thing.
As for the parts to do the job, this is a list off the top of my head to do the suspension and brakes (with my personal preferences added):
Front brake rotor (Name brand. Whatever you buy get a U.S.A made rotor)
Front brake pads (name brand; Wagner or Raybestos)
Front brake caliper (if necessary; it's been a while since I had to do this, but you used to be able to get loaded calipers w/pads. Raybestos used to do this)
- or-
Front caliper rebuild kit (the front calipers are very simple and if it just needs seals you can rebuild them yourself for really cheap)
Front brake hose (Wagner or Raybestos; if your hoses are from 1987 then they're 25 years old this year)
Front Wheel Bearings Inner & Outer (I prefer Timken; sometimes you can save on them by going to a bearing supply store)
Front Wheel Seal (National; also check for them at a bearing supply)
Front Axle Shaft/Spindle Bearing, Oil Seal, Thrust Washer & Dust Seal (I can't recall the brand. Goes inside spindle to seal axle spindle to front axle shaft)
Front Axle U-Joint (Dana/Spicer)
Upper Ball Joint (Moog; they make one with a side mounted grease zerk which allows you to grease the upper ball joint. Otherwise greasing the ball joint can be a chore).
Lower Ball Joint (Moog)
Tie Rod (Moog)
Outer Tie Rod end (Moog)
Drag Link Ends (Moog)
Sway Bar bushings (Energy Suspension Polyurethane)
Spring Bushings (Energy Suspension Polyurethane)
Shocks (Gabriel or Monroe if no lift kit)
Front Steering Stabilizer (attaches to tie rod; Gabriel or Monroe)
Tools to do the job (also from the top of my head):
Socket set and ratchet
Open/Box end wrenches
Line Wrenches (especially needed if you're going to change the front rubber brake hoses)
Snap Ring Pliers ( to remove snap ring on the end of the axle shaft)
Hub retaining Nut Socket (to remove Hub retaining nuts from spindle
Needle Nose and Regular Pliers ( to remove cotter pins)
Breaker Bar (can help lend some additional torque to get stubborn bolts/nuts moving)
Torque Wrench (if you're going to torque everything back to specs)
Dead Blow Hammer (to persuade spindle to free itself from the steering knuckle)
5 lb Hammer (to rap on axle tube ears to assist with removing knuckle/ball joint assembly from axle tube)
Allen Wrench set (to remove allen screws on lockout hub)
Brake Caliper Hex Head Socket (don't remember the size; to remove brake caliper bolt - can use appropriately sized allen wrench)
Grease gun
Grease (Hi-temp disc brake grease for wheel bearings and hub parts)
Anti-sieze (for any bolts that are exposed to the elements that you don't want to seize up)
WD-40/PB Blaster (to assist with loosening any seized nuts or bolts)
Bearing Grease Packer (helps to pack wheel bearings and keep your hands a bit cleaner)
Nitrile Gloves (also helps keep your hands clean)
Spray Brake Cleaner (to clean the rotor of oils prior to installing brake pads)
Rags/paper towels (self explanatory)
Jack and Jack Stands (Safety first - do it right and don't use bricks, cinder blocks, etc.)
Ball joint installation/removal tool (you can rent the tool or have a machine shop press them for you)
Tie rod removal tool (you can also rent this tool at most part stores; I think it works better than a pickle fork)
Fish scale (recommended by the GM service manual to check ball joint adjustment. 25 lbs to pull the knuckle to the left or right w/o the tie rod attached. The preload sleeve in the axle tube will need to be adjusted if out of spec.)
Bearing Race/Seal installation tool kit (really useful for installing bearing races, bearings and seals squarely into or onto their respective bore)
Brake Caliper Bolt Lubricant ( for lubing the brake caliper bolt)
Brake Pad Anti-squeak /spray adhesive (optional stuff to make sure the brake pads don't rattle on the caliper)
Upper Ball Joint Adjusting Sleeve Spanner Socket (used to loosen/tighten the upper ball joint adjusting sleeve to properly torque the upper ball joint prior to installing and torquing the upper ball joint nut)
Chilton's Repair Manual or 1987 GM truck service manual (Chilton's from the parts stores, GM manual from swap meets, ebay, book sellers, etc)
I'm sure I forgot something, but I think this is a pretty complete list for the job. It should go pretty smooth if you can get a shop manual and read through the steps a few times, look at the various diagrams and be familiar with the process before you disassemble the front end.