Don't know what you would really gain from restoring the playfield & clearcoating it. There's a point where you are doing things "just to do them." After it's clearcoated, which it already is, how different do you think it will be? Maybe you get it back and it just doesn't play like it used to, and then you spent money to do it.
EDIT: Basically I'd think about it this way. You're machine sounds like it's 95% perfect. How much time & money so you think is reasonable to spend to sit back and say "YES! It's 4% better now."
Time and money that could be put better on a new machine.