Normally I would side with you on changing out a rear main "while you're in there".... In this case though if the engine has been running and it's not dumping oil from the rear main I'd leave well enough alone. It may be that the existing seal could provide a better seal than anything you could hope to install today. Besides that, installing a new rope seal insitue can be a bit tricky. Special tool required as well. Search "rear main seal" and "rope seal" on here for more info the subject. RockAuto.com should have the rear main seal listed for your engine.
As for the clutch either stack some washers under your bolts to make them short enough or just loosen all of the bolts holding the pressure plate to the flywheel a few turns at a time. It's really not that time consuming. With respect to the inspection cover I don't recall seeing a seal there either. Just make sure it's clean and reinstall it. There is a cotter pin installed in the hole
In the bottom of the cover. Someone suggested a while back that the pin was to prevent insects from making homes inside the cover while still allowing any oil build-up to drain freely.
http://www.hansenwebdesign.com/truck/facts.html In the "files to download" section you will find parts and repair manuals if you don't have them already. Most part numbers can still be crossed using your favorite search engine.