Best to call Charter Arms w/ a serial number. Most likely +P is NOT OK in an older gun, but I would contact the maker.
I would probably stick with a 38+P rated new gun, if buying, but your current gun is not lacking in anything.
You might also look at Kel Tec, since you are familiar with autopistols. I'm debating the P-32, P3AT, and P-11. I like the idea of more bullets than 5, and the P-11 is actually a little smaller and lighter than most 5shot revolvers. BUT, the 32 and 380's are a TON smaller than the 9mm....DILEMMA!
Anyway, sounds like you got a good gun already. If you want a new one, by all means, go ahead, it would definitely be +P rated.