Hi, the article Cruiser2B mentioned is in the May/June 2011 issue and is by Joe Steinberger. His DIY system was rather different than the $$$ systems Practical Sailor covered around the same time.
Aside from the resources mentioned, the listserve electricboats : Electric Boats
is full of information and has many people who converted their boats, who sell the systems, and those who are just learning about it.
I think the biggest factor is the range you need. If you need ~100+ miles fuels can provide, electric is out of the question. If you only need a few miles, a low cost system like the one in GOB could do it. Electric motors have enough power
for short bursts through inlets, but have trouble storing enough energy
to run for long periods. That said, if the range works for you, which it could if you don't spend time in narrow rivers and channels and have some patience and flexibility, electric offers a lot of advantages such as: silent operation, no trips to the fuel dock guesstimating fuel so as to have enough but not having it grow old in the tank, no antifreeze or oil changes each season, and potentially extra space where the motor, transmission, tank, exhaust, and water intake used to be, and to repeat that last one, you get to remove a hole from the bottom of you boat
I've just put a deposit down on a system for my Ranger 33, and am going to fit the batteries in with the electric motor where the old A4 was. I suspect it will weigh about the same as the old system, but with the weight near the center of gravity and none out under the helm seat where the old fuel tank was. It's been helpful to have a friend who converted his boat last spring. See if you can find a local on that electric boats listserve. I highly recommend searching the archives and asking questions there.
Best of luck!