Back in August my boyfriend blew my transmission in my 94' z28 and him and my dad, instead of fixing it, got me a "temporary" one out of a junkyard from a 94' Firebird. My dad assumed it'd be a good tranny since a specific company had rebuilt it and left their name all over it. Okay, a few weeks later this transmission starts getting funny and eventually starts to flywheel at around 4-45k. My dad calls around to find the best price to get this one rebuilt and low and behold the place that the transmission came from tells us $1200, which is the lowest. So we go to drop my car off yesterday and the guy says "I'll have my guys look at it but before we take anything apart we'll give you a call for a quote". Okay, great. I get home at 6pm last night to a call saying that my tranny is apart, in 10 boxes to be exact, and that it'll cost $2500. I was upset because I had saved up $1200 for it, and I refuse to get a car back that doesn't even work. He says it'll be $300 to just pick it up and I'm mad about that too. He was also very unpleasant on the phone which made it harder to deal with.
To make a long story short... Where can I get a 4L60E rebuild that works for $600-$1000 or where on Long Island is there a company that can get me a rebuild for around $1200? I would name the place that did that to my car but I am trying to be nice about it.
I really don't even know what to do.

I'm pretty new to this and any help is greatly appreciated.