I think I'd rate that one a 2 for the actual work, but a 4 for overall complexity. The difficult part is the fact that, since it's your countershaft seal, you're going to have to split the cases. I've heard from some here who've said that you can nip off a tab from the new one and drive it in place of the old one, but considering the old one was installed before the cases were put together and it's lasted this long, I'd suggest following the factory's lead.
Drain the engine, pull the engine, flip it over, remove the bottom case half, replace the seal, put on a new case seal, and put it all back together. A goodly weekend job if you're handy, a week of evenings if you're not. Make sure all your parts and tools are lined up beforehand and save yourself some heartache and waiting.