Lots of good options mentioned. Renting/borrowing makes sense to me if you're pressed for time and tight on cash.
I agree with agedhorse that you should check (or have someone check) the cabs to make sure that they're sound.
Re. your friend who's anal about letting others use his gear, tell him that he can come to the show if he's worried about it and help set the levels, etc. If the cabs are in good shape and he only needs to loan you an amp, that should put his mind at least somewhat at ease. Your choice, of course, as to whether you want to deal with him or not.
If you're able to buy something reliable and sufficiently powerful to cover your gig without overextending yourself financially, that could make sense as well -- even if it's not your favorite thing ever, you can play it while you look for something you like and then sell it. If you get a good deal on it, it might even make sense to keep it as a backup.
EDIT: You might also call or swing by the venue to see what, if anything, they'd have for you to play through.