Kudos for the enthusiasm! I made the jump four years ago, and don't regret a minute of it. Learning good double bass technique really cleaned up my electric technique too, I highly recommend it. Rufus Reid's The Evolving Bassist is a must-own book and will give you a good foundation. I suggest finding a teacher too, at least for a few lessons until you have enough knowledge to practice without causing injury. I haven't ever played an electric upright, but since you can have the action pretty low (and have the preamp take care of the volume) I assume it's a bit easier on the hands than knocking out a huge sound acoustically.
Some other great books:
Bille's Nuovo Methodo
Simandl's New Method for Double Bass
Ray Brown's Bass Method
Best of luck!
Chris