Actually, let me give you a responsible answer.
Go to a dealer, any dealer that has a 330 manual on his floor, book a test drive, drive it and then compare, you'll take the manual im sure.
Fixing your box is not an option really, 25k is hectic and in my view not worth it.
A scrapyard box may last 10 days or 10 years, you have no idea of knowing, and you only get a 30 day warentee from the scrapyard if that, and its going to cost you about the same (maybe a bit less) then a manual conversion.
Also, the 2 to 3k labour involved with stripping out the boxes if something does go wrong.
My view you have 4 options.
Manual swap 10 to 15k (cheaper if you source all the bits yourself, I can try and help with the electronic bits)
Fix your box for 25k (not an option in my view)
Scrapyard box 8 to 13k (with no warrentee)
Sell the car for the 50k and be left with nothing (dont know if you owe anything)
I'd go for the manual swap, and you dont need a warentee on that, as those boxes generally do not break.
