Just like to say, I have no experience with R/C, besides a few cars, but I'd like to get involved. To be honest, I enjoy building as much as driving cars personally, but boats do seem to be a bit more entertaining. I'm wondering, are all the hulls sold in one solid piece, or do any of these kits require any work that isn't more or less mechanical?

There are plenty of wooden kits out there for building yourself depending on exactly what it is you want. Lesro models sell a few old favourites of mine, dont know if they are available in the US. Many hulls these days are moulded ABS or GRP which only leaves you to finish them off with paint, radio, and engine. Boring! Hulls you build yourself often offer more scope to fit the engine you want rather than the one it was designed for too.