Bwhahahahahahahaah, your'e 23 and you're fucking around with an old E36? Dude just ditch it and buy something better.
And $108 an hour labor is overpriced, find a real mechanic shop. I had a shop swap out a transmission on an E36 and I only paid $250, providing all parts plus Pizza.

It's not a 12 hour job, it's more like 4-6 hour depending on skill.

Sell the damn thing and get over it.

How much did you buy it for?

Even if you fix the engine, it's still 150K+ and has been abused since it overheatd.
Transmission is an automatic and will fail within 20K due to lifetime fluid fisaco.

It's a lemon, you bought a lemom. Wow.