Does my trans need a rebuild?

[team39763]

I took off the aluminum pan today to install my RMVB. When I got it off, it had some dirty dark looking stuff in it. Is that clutch material?  There was also small paint chips(probably from the old pan) and small chips of aluminum.  I found a clump of what looked like paper fibers and debris above the valvebody.
I had a local mechanic build it for me with a kit with alto red clutches and koleen steels, hardened sprag, 4L60 low/reverse thingy(don't remember the name). I also added a remote mounted filter and a 40,000GVW cooler. The stall was a 9.5" 3500. The truck was driven only a few times here in town(50 miles or less) and only seen 5 passes down the track(no burnouts). It's a slow 12sec truck, so it wasn't too hard on the trans.
What should I be checking next? I don't know anything about transmissions, so I can't build it myself at this time.

[joesgarage71]

 Your gonna have some trash in the pan, but you say its been rebuilt not long ago? Ain't it shifting right? I'd be talking to the guy that rebuilt it.

[team39763]

Well actually, it was built a while back...I think 2 years, but I haven't driven it much.  It shifted fine and everything.

[joesgarage71]

Don't worry about it then,

[team39763]

Another guy told me the same thing.  He said it was probably trash and stuff left from the old converter, cooler, and lines.  I'm betting the fibers were from the new paper gaskets installed during the rebuild.  I got everything put together today and I'm almost ready to put the truck back together...just waiting on some decent weather.