Thought this couldn`t be fixed but gave it to friend with lots of patience. The tripmeter shaft was bent and couldnt turn. The face looked like a dog`s breakfast and there was glue all over the mating surfaces showing previous owner had tampered with it.

After the repair. He did a nice job. Never think these gauges can`t be fixed.

Result

Hey, do you have any advice for getting into one of these without mangling it? And a good way to get it back together?

My advice is if you don`t have patience don`t try it..I gave mine to someone with plenty patience to fix. There`s no other way but to carefully break them open using a sharp Stanley knife, do the repair inside and glue back together again. The workings inside require even more patience and very small tools to get sorted.