do a compression test, it doesn't sounds like a head gasket problem & the only way water got into your spark plug hole was from the top while u were washing it.. dry it out as much as possible, pull the plugs & make sure they are ok, change them for the hell of it if u want to be sure just coz they are cheep. then look into your vacume leak problem could be anything from a hose to the TB & IM gaskets as already stated by others.

just keep trouble shooting & you'll get it figured out from process of elimination.

To answer your other question. No, a head gasket job is not something i would recommend for a first timer, almost everything has to be tore down to get the head off!

best of luck to ya, keep us posted