I did that recently. It's not too bad, but will be a little expensive if you use all the factory stuff. Assuming your engine already has electric start? If not, forget it and just get another engine! The cost of the starter and components alone negates the conversion.
Boats.net has all the little bits and pieces you will need under the cowl. Mine is a 25, so it's a little different and I imagine that the parts under the cowl that you need will be different as well. On mine, I needed a bracket to hold the control cables, a plug where the cables enter the engine, and a bell crank, various rods and some cable ends for connecting the cables. I used seastar extreme cables, a Uflex side mount control and Uflex rotary helm with Uflex cable. I also made my own engine wiring harness using the FSM and an after market keyswitch and lanyard.
Like I said, if you use ALL the factory stuff, it gets expensive fast. If your not a DIY kind of guy, just sell it and get one that is already setup for it.