How hard isit to change alternater in a lincon ls 01 w/ 3.7 v8 an whers it located? 1 to 10 scale,?

With 10 bein hardest........ And where is it located ? Also what had happened is the batt was dead on it when I test drove it an ran great. Went back to show my fam and ghad to be jumped agsin bcus battery is bad an needs replaced. Well the kid from the lot got the jump box an had the terminals crossed when I tried to start it an it jus clicked an white smoke came out from under hood. We put another (used) but good battery in and it started fine an drove it for a min when it jus shut down. No lights or anything electrical. Got it jumped from a vehicle and the cables were exremely hot!!!!!!! It started up and died as I got it back to dealer. I'm thinkin its alyernator. This car ran perfect!!!!!! And the dealer said he will fix it and the price we agreed on stays same or sell as is and drop 1000 off!!!!!,,so is this sounding like the alternator seeing that it runs when it jumps but dies shortly after? Or much worse? Car looks an runs great an 1000 off would be nice cus I found a alternator for 50 dllrs and me an my old man have changed quite a few..in montys, luninas, cavaliers etc....but I really like and want it but could more damage been done and again where is the alt? And how dffucult to change? ........thanks for reading