My backyard mechanic stole the engine from my 2009 Hyundai  Elantra Touring automatic it had over 200,000 miles on it and replaced it with a 2006 Kia Rio engine. Car blew head gasket when I got a Jumpstart after driving 50 miles car would not start because they put dirt under the cell battery covers which killed my brand new battery. I know some of the parts they switched out like the alternator water pump etc. I need to figure out what might have still worked or would everything like the computer etc have to stay with stolen engine for it to still work? Also I was considering buying a used engine with warranty and I would have to buy alternator etc. Would this be cost effective for engine and all parts needed? My car was in excellent condition body looks brand new this has been a nightmare and proof there are Evil people in this world as they did it on purpose. Heart Breaking.

Thank you for any help I receive.