Find another garage.
I can help; I'll take over your loan...
Unless you let the battery run down dead a few times, or unless it has been overcharged, there is no reason to replace it in less than about 5 years.
Rebuilt alternators are sometimes not built to the same standards as new, and have much shorter life.
Finding a scrupulous mechanic who really understands electrics and electronics is difficult, if not near impossible.
Good luck.
GB | 
