Can't help with the shiftier hitting the ignition switch.
Using this forum and being you said your visual, using search engines will help you a lot in repairs, using your favorite search engine, copy and paste Fixing Shift Indicator (P N D 2 1), Late 1980's to Early 1990's Chevy Chevrolet GMC in the search box and look for a video showing what you need for the shift indicator.
On the vacuum device, it's been 40 years or more since I've seen one, and sure they changed the design over the years, but this looks like it is a vacuum motor for the exhaust manifold heat riser dampener found on the very back of the right exhaust manifold, when the engine is cold it directs hot exhaust air up through the intake manifold to help it idle better till it warmed up.
If i'm mistaken on this, someone may be along and correct me, then we both will learn something