Cost at most chain stores can be crazy expensive for what you get. I was in a somewhat similar situation a couple of years ago. Mine was a total rebuild from headers back. Local guys were crazy high, mostly because they had to include the catalytic converter. If you decide to go that route I can say the system I bought from Corvette Central was a simple bolt on. Everything lined up beautifully. Mine is an 81 so I can't comment on your year except that I have seen good things about that system as well. The complete system was $650 shipping included, i think it's about $100 more now. I've never attempted to clean up a system and repair it. Usually by the time I should fix it, it's beyond fixing and time to replace.
______________
Dave C..........My mantra: I can not be bought!! Long and short term leases available.
In the words of Zora Arkus-Duntov "Is your seat belt fastened? Alright, Let's go"
Yeah, I know, Shut up Dave.