Can the rear seat of the 98 club cab be removed? If so, is it easy to do?

It went in, it can come out. Probably depends on how much time you're willing to allot to remove it, and how important it is that you do...

I don't know about the 98 but my 97 back seat came out fairly easily by lifting up the seat and into the locking position and removing the 4 bolts holding it to the floor and lifting it out.

Got a sawzall???????????