hello. I live in Southern California nd I'm considering my first Alfa. It's a 74 1750. i was wondering if the rear plastic window can be replced or if the whole top needs to be replced when the rear plastic window is no longer good. What is the average cost for a new black cloth top? Thanks! I hope I get this car sometime next week. Also, what are the common issues other than rust, that I should lookout for in this car? I'm stepping in from the world of Porsches and I'd really like to know this car a bit better before I pull the trigger. once again Thanks!