$425 sounds about right to me unless it's got night sights or something extra. Used, police turn-in G22's go for around $380, so it would be hard to get much more than $425 for yours despite the fact that it's in like new condition. I bought my 22 from J&G sales for $379. I also just bought a like new G26, with 3 mags and the original box for $400. But heck, ask $475, you never know, you might get it!
If you're used to a Glock why switch? Trade your G22 in on a G23 or G27. It's hard to beat a Glock for CCW, they're light, flat, super reliable, have excellent capacity and don't suffer from rusting that sweating all over them will cause. I sweat all over my carry gun here in Arizona, specially in the summer time, I've even started rust spots on stainless guns but I've never seen a speck of rust on one of my Glocks.