Replace headers with stock manifolds and a carb question

[1stimer]

Hi guys. Mechanic says I have some exhaust leaks, and says headers need to be redone...(I guess gaskets and bolts).

I want to learn to tackle some of the issues that I need to in order to get this old girl running correctly.

Is this something a novice DIY'er could do?

The truck is more of a "hot rod" than I would like, and was thinking going back to a stock manifold might cause me less headaches and get the truck back to stock like I would eventually like it to be. Any thoughts?

Also....I don't know if it is a 454 or a 402.

I did notice one header bolt is completely missing. Would this be enough to cause an easily detectable leak?

Mechanic says carb is the wrong size for the engine. It is an Edelbrock Performer 800 CFM. Is this carb too much? Is it worth anything used (less than 1 year old)? Would you go back to a stock carb or stick with a 'lower' specd aftermarket one?

Thanks for your support guys....I'm trying to learn.

Randy