keep ammeter? / hack job

Where the green wire is "attached" to the bulkhead it appears that someone used the female end of a clip, crimped it, and stuffed it in there. Now it has come out and it is all green and corroded in there. So, two questions:

1) How do I fix this correctly?
2) In reading about ammeter problems, alot of folks say it isn't safe. Is there a way to keep the original ammeter and make it safe? I like it all original looking but a burnt up dash doesn't count as original to me.

That looks like a mess.................. I wish I could help.............Is that the key hot wire..im not sure