GooGone isn't going to do it, not strong enough. Xylene works well, get GOOD rubber gloves and use it outdoors. You have to sand the isht out of the cabinet; it has to be PERFECTLY smooth. Go up from 100 to 150 to 220. Then seal it and 220 again. Before decals, vacuum or brush and tack cloth. A tiny speck of dirt will look like a ripe zit on a 15 year olds forehead.

And you'll probably want to get the playfield and all the hardware and guts out of the game before proceedin further

Xylene, gloves, get the cabinet side you're working on horizontal. Dampen a shop rag or paper towels or pour a puddle and spread the product over the surface. Let it sit for a minute or two and it will dissolve the remaining glue. Change the surface of the shop rag or use another paper towel to wipe off the residue. No rinse, it evaporates but you have to wipe off the glue reside. At that point you can fill in any holes, dents or scratches, and fix the corners. Then sand 100-150-220, you can blow/vacuum/tack cloth the dust off. If you are putting the decals on dry, no need for sealer (but it can't hurt). If wet, the sanding sealer will prevent the spray from raising the wood grain. If you use the sealer, light sand 220 and then decal.

Lots of quality videos out there, google is your friend.