Roger, I was a guitar player first, like you. When my B-3 playing partner retired, I tried 8 or so keyboard players and finally decided to do it myself. You have a real advantage, since you understand structure and will be able to figure out the material you already know on guitar on keyboards.
If you do a OMB act, keep the guitar for variety. You may have to switch to an acoustic or hibred, but it's a nice change of pace. If you were a lead player, many I know sequece some tunes and play over them.
A GOOD attitude is not that you switched to OMB but expanded your involvement to include OMB. It's really nice to play a gig with other players once in a while.
If the money is right, I often add a player or two just for the interplay.
However you decide to do it, stick with it and you will be much better off for the experience.
GOOD LUCK!
Russ