Chainsaw Repair

wow that was a bunch of work for you thanks.So where do you buy yours? You said the bearings can be bought a lot cheeper where? Next subject Today I worked on a 500 i bought last night the guy fell a tree on it i think.The alumnium handel to the D handel was broken, the I del screw was broken off from the carb ,the plastic shield behind the carb was broken. So this afternoon I went to work on it and got her all fixed up runs great. I noticed somthing ( 1) the case is Black not yellow ,and (2 )  the sproket is a large star shaped one not the small slotted kind i have on all my saws and (3) the chain appears to be maybe a 3/8 ? the drivers say 21 on them wher all mine say 325 ? I have a few other chains I have picked up over the years and they say some other number on thier drivers, If I tell you the number can you fill me in?