Well... if you're willing to R&R yourself (or have a resource who'll do it for less than $800) - check out
www.car-part.com
I see one for a 2007 Ranier 5.3 in S. Dakota for $100. There are others, too - that's just the first one I saw.
You contact the location you want to purchase from; they validate the part and give you a shipping quote.
You can search on other models that might interchange (like our TrailBlazers and Envoys) or just search specifically on Rainiers.
As far as the boxes going bad - check to see if you don't have a short somewhere. There are threads here describing owners who thought they had a bad box - and many times, they found a cut or bare wire.
AFAIK, there's no open recall on these (and wouldn't be unless a 'safety' issue was at large (like starting fires, etc.))
If you need schematics, check out any post by Mooseman - he has links to them in his signature.