Kevin, to answer your question about manuals, what Terry posted is all that's in the PC1924 service manual (covers LT133, 155, and 166) on drive belt R&R. The manual does not show belt routing.
The job is fairly straightforward, as Fred has noted. Once you get out and get under your tractor, you can see where things are. You'll need to drop the steering rods and pop the big springs that block R&R of the loose belt.
You'll need a lever tool to get the big springs reinstalled. The one I use is a Bendix-and-Lockheed automotive brake tool that is about 18 inches long with a U-shaped end for installing shoe retracting springs.
I'll also agree with Fred that you should get new idlers along with a new Deere belt. The bearings in them get tired and noisy, and if they don't need replacement now, they'll probably need it next time around with the belt.
Hank