was going to respond a couple hours ago, but i'll just echo what others have said - system 80's will be more of a challenge to work on as a first pin. if you got one in really awesome playing shape, then i'd say go for it and learn as you go if you're really into the game. however - how far do you want to get in pin repair? does the aspect of repairing really interest you, or do you mainly want to play them and only fix as necessary?
i will also echo that classic bally's (-35 in particular) are a great starting point into the SS world.
do you play a lot currently? might be worth getting in touch and in with FSP to experience a bunch of games first-hand.