Need Help With Quincy 216-40 Compressor

I'm trying to troubleshoot and repair a Quincy model 216-40 two stage air compressor. I've re-built large and small engines before but no compressors. My hesitancy in tearing into is is 1) I don't even know what makes it work, 2) I don't have a manual or parts breakdown, 3) I would prefer to take it apart after someone can suggest where to start first and can reasonably assure me that parts are not going to start falling out on their own. The problem started a couple of years ago when it started overheating for no apparent reason. Since then I just used it by keeping a box fan directed at the air fins and only running it in short cycles. Also the air output volume seems gradually less and less since that time. I have removed the air cleaner and removed the outlet plumbing so I can inspect the check valve into the receiver. Check valve looks OK. I did remove the pipe plug to the oil pressure controlled unloader valve while it was on the compressor but as soon as I backed it off I saw there was a spring in there so I didn't take the unloader valve apart at that time. Someone told me there's a steel ball in there that needs to be very clean. So after I found out it was safe to remove the unloader valve from the compresor crankcase I took it apart and cleaned it but unless I'm doing something wrong, the steel ball doesn't come out. Now the compressor doesn't pump up at all. The unloaders don't appaer to be kicking in. There is good oil pressure and some pressure on the outlet side of the unloader valve but I don't know how much pressure or volume of air the unloaders need to function. I also don't know thats its an unloader problem at all since It could be a problem with the valves in the head. By the way, I did re-assemble the unloader valve correctly. Submitted by Charles Neff, from TX