Well, I got lucky. I called a good friend; the dude helps everyone out, and as a result he has a lot of contacts and people willing to help him out.
Anyway, his "guy" is the lead mechanic at one of the local Chevy dealers. Said "guy" works on the side for extremely reasonable prices. He quoted a good price to install my new core plus the flush and discharge/recharge of the A/C. Quite a bit cheaper than retail mechanic prices, but he said he's done it on this truck many times and can knock it out in half a day.
The bad news, if there is any, is that he's backed up for 2 weeks and the temperatures are dropping.
By the time I'm done I'll have a brand new 13yr old truck. LOL