Pretty sure ddstoys will have some good tips for you as he just brought one of these back from the dead.

Me personally i'd advise you judge the backglass for yourself.  Take a look at the back of it.  Most of them are pretty flakey.  One persons "Good" is anothers "Hammered"

Couldn't really see a nice functioning one of these going for more than 1200 on eBay.

I'd probably hold off for an early SS Bally or Stern from the same era.  As your first project an early SS Williams might be a little harder to tame, as they are pretty temperamental old girls.  However, YMMV