I agree about finding another exhaust shop, a basic single exhaust if you just need something to get you by, should be pretty cheap.
Yes, horribly undersized for your engine, but 2.5" single tube run I can't imagine should cost anymore than about $200 installed. Again, talking temporary until you aren't broke anymore.

I don't know what the going rate is for 3" pipe, I expect it's a fair amount more than 2.5" stuff. If the price is very similar, 3" would be the way to go though obviously.
If you've got stock pipe pieces that you can use to cobble together a system, Napa sells exhaust pipe bends and adapters in multiple sizes, so if you just need a few pieces to put some existing pipe together, it wouldn't be but $50 or so. But if you were trying to do a WHOLE system with bends over the axle and what not, that method would be expensive. You'd still need someone with a MIG to weld it all together for you.
I used the stock exhaust that was on the truck, four 45* exhaust tips, and two 2.5" ID to 2.5" OD adapters from Napa to get my system adapted to headers.