Seal it or Strip it?

hey guys whats up, I stripped my truck down to bare metal and primed it with some PPG DP epoxy primer, i'm bout to bring it up to my school to paint, now what im wondering is since its been out in the weather and i know it has absorbed water and shit so im wondering if i should strip the primer and start over with bare metal or jus sand it and seal over it....i asked me professor about it and he seemed to think i would be ok with jus sealing over it.....jus figured i would get some other input on it