The cost of a rebuilt engine for a 2001 BMW 325i

Around $5,000 maybe more , then there's the tranny that's just as old , another $3,000 ,

Some just replace the engine due to the labor to replace the parts. The above prices are on the low end, it could be much more. Do you want to dump that kind of money into a vehicle that is worth a thousand?

I would budget at least 10 grand for the engine. I would look for crate engines.