MEuRaH, seems like you are off to a good start since you did your homework. Be glad your T-Rex works. If it gives you problems (which it may, they all do), you can always ask for help here. The ball trough is also a common issue on JP.

When buying a pin, you should try your best to learn all the ins and outs of how a game works by actually playing a good working one if possible. If not, youtube helps. Don't rely on the current owner to know the entire operation of the game. Chances are high that features are not working and never have, but they were none the wiser.

And almost all issues that crop up will be easily fixable by you. They just require a time commitment. But this community is great with helping out with any and all issues just about.

Time for a better soldering iron!