2004 Cadillac SRX V8 w/towing package. 111,000 miles. Mostly Dargie Delight and Reggie Hamilton passengers, not really any towing at all. So coolant has been leaking slowly, and just yesterday it leaked all the way gone in just 1 short 5 min. drive. "Engine hot" thing came on and it said to pull over. I let it cool down and went back and filled it again, and it did the same thing to me. I managed to get it to the dealer, and they say it's needing a complete replacement of the radiator, not the coolant tank like I thought. Well they want $900 after parts and labor. I can get one for like $250 it looks like (suggestions welcome) so I could save a ton by doing it myself. I have another car to use in the meantime. My question is: Is this something a mostly novice should attempt? Are aftermarket radiators ok or is there a reason to get factory?