Especially if you have another (likely older) vid card laying around that will fit into your PC slot or have another PC you can use, for the time being until they make their decision - yeah, I'd say "go for it."
Do you have a back-up video card just say laying around? I always keep parts around. I kept my GeForce 6600 GT around in one of those special bags and all, just to have a spare part laying around for whatever reason - say a part fails (8800 GT failed, in my case) and I need to install a "hold me over" video card (that is what happened); or I decide to say move my 8800 over to a newer PC I might later buy and want to put the 6600 back in this aging PC. You just never know w/ these things, you know?
Since you have a BFG, chances are you got a Limited Lifetime Warranty.
There's no reason for your card to be acting up, if you ain't at fault in any sort of way (like the stuff I mentioned a few posts above). If you ain't at fault, it should all be good, man!
What's the worst that can really happen?
You either wind up w/ the card you sent them back, not repaired. I'd doubt that, though.
They'd probably fix it/repair your card, at the very least.
They might do you what they did to me - send you another of the same card; either new or refurbished. They might just send you a different refurbished GF 7900 GTX. Who knows; they might send you a new one. Anyone's guess.
Or like Pug said - maybe they'll send you a better card. That'd be mad sweet.