9/16 and 5/8 should cover either leg bolt/head bolt possibility.

5/16 allen for the coffin lock

Just bring a socket set! Do you have a dolly, straps, blankets, cardboard? These things are heavy -- 250lbs. Also suggested that you remove the balls from the machine. Here is one thread: https://pinside.com/pinball/forum/topic/moving-a-pin-1

Congratulations! Monopoly was my first machine too. The theme is a bit aseptic but overall it is a fun game.

Open it at home, keep any quarters. Only need a big allen key to lower the head. There are no head bolts. Keep the game flat if you don't drill the lock to remove the coinbox and loose bits.

With no key on offer there is a chance that the item is not being sold by the owner.