So you've never turned a machine on and don't know how to check fuses/board connections? No offense but I'm surprised at how many people dive into getting their own machine yet don't know the simplest things about it. Please don't take offense from this, it's just better to have some knowledge/experience up front so if something fails it won't be too difficult for you to assess later.

Glad you snatched it up, what a great find! Do you realize how difficult it is to find a backglass in that type of condition? Cheers to your first machine! I know it's a crash course for you but it's also a stellar start to your collection!

The batteries are just like anything else with batteries, but for the record I doubt they will do anything dangerous if you put them in backwards. There will simply be no net charge and thus, no electrical current.