I was able to get away from work early enough yesterday to get the Trek to the bike shop three towns away . I spoke to them today and the mechanic confirmed it is the shifter that needs to be replaced. I will pick up the bike, ride it this weekend, then drop it back off on Sunday. The mechanic will order the shifter and work on it next week. Hopefully all will be well.
You hit the nail on the head guys. Thanks !
I'll let you know after all is done if the problem is solved.