Lenny if you have a 742 chunk it doesn't use a crush sleeve. It has a solid spacer and uses shims to set the desired bearing pre-load. There is only one center section gasket. The one that the 3rd member mounts to the case with. It'll probably rip up when you remove the 3rd member so you most likely need one. I've used Ratech stuff and it is decent quality stuff. I also used a set of Motive 3:73 gears last year in a 742 case and I couldn't get the setup right on and they howled some. Won't be buying them again as all the other brands I've used (Richmond, Yukon, and Dana) set up properly and were quiet.
Also you might try Dr. Diff for the parts as he sells Richmond gears for about that same price and I think the setup kit is a few bucks cheaper.
BTW: If yours has new bearings in it already why are you changing them? I'd go for the minor setup kit and save $60~70. JMHO