As for how to handle Wesley having a gay relationship, I'd say the point would be to do it the same way his heterosexual relationships were.
The second season episode The Dauphin would have been a good choice, replacing Jaime Hubbard with male actor. The episode was non-sexual, there's (iirc) a single kiss. The storyline deals with Wesley's feeling of love and attraction for Salia.
I'm not sure, but I believe this was Wesley's first romance.