Having built both the Model Slipway and Speedline Tamars, the Slipway version is much easier to build, although the cabin structure is a challenge.
The Model Slipway has excellent instructions and guides you to the finished model, with a methodical approach there are no big worries. Don't forget M.S. have excellent customer support.
You need 4 channel because a bow thruster is a great advantage.
Go brushless with LiPo's and a heavy duty coupling. If you decide to go brushless, we can advise you further later on.
Five blade brass props are best kept for display, it runs much better on 3 or 4 blades.
The finished model is very robust...
http://www.youtube.com/watch?v=SBH89_6HDU4