I troll every now and then for walleye. It's another way to fish while I'm moving to another spot (my boat's not a speedster, so if it's gonna take a bit to get there, might as well fish my way there). My boat's 12' - I'd love to have the room of a 16'er.
Not a whole lot to it - get some rod holders you like, get some inline planer boards (the mast kits are nice for big water, but unnecessary for walleye IMO), a few line counter rods (again, not necessary but man oh man do they make targeting depth easier), and go for a drive.
My very basic setup compared to guys that do this stuff constantly:
Rod holders - I'm torn at the moment between my Scotty holders (will probably keep them) and picking up a set of Driftmasters
Planers - Offshore Tackle
Rod/Reel - Either the bright yellow Starfire Eagle Claw trolling rod or Diawa Wilderness, reels are all Diawa LC's.
Other than rod holders, you can pretty much longline without the need of planers if you're only using a few rods (left/right/rear of boat) - so don't think you need to get everything just to go trolling.