sbdsr
Newbie
Most've it's been answered. Coolant temp sensor in the head, the melted black cylinder is the solenoid on the EGR valve, the right hand tube is the one that leads down to the manifold (if I remember correctly) and the bulge you have pictured is a check valve (with engine running there should be no exhaust gases coming out, if that valve failed it could've caused the melty melty, normally connected with a rubber hose to the tube on the left). Unless you need to meet emissions requirements you can remove all of those air injection lines and plug the manifolds.
Factory GM Service Manuals exist, I think it's a 2 volume set for 1996, they come up on ebay occasionally and are totally worth it.
Delco Platinum (gapped to .060, double check emissions sticker underhood) plugs and tune up parts to answer your other question. Don't bother with iridium, double, triple, +4, split, all gimmicks. In stock form Vortec engines love OEM parts. The only exception is the GARBAGE OEM fuel injectors on the 454, for that look into the Blue Knight injector set from FiveOMotorsports, the sell a kit specifically for these engines.
OEM parts, Like in GM..... as in Dealer....or is there some other place other than online that I can find them, that's not going to screw me over like the dealer....