1. You NV5600 does not take Amsoil MTF, so don't order it. You need Amsoil 5w30 HDD Series 3000 oil (4 qts).
2. Get a 17mm Hex Key. Remove the the fill plug. It is behind the drivers side PTO cover about half way up the transmission.
3. Remove the drivers side PTO cover (six bolts). The fluid will begin to drain when you remove the bottom bolts, but take the cover completely off. After removing cover, reach inside and you should feel a magnet. Take it out, clean it, and reinstall it.
4. Clean the gasket surface of both the PTO cover and where it mounts to the case. Reapply a good quality gasket sealer (ultra grey works great). Wait about 10 min then reattach PTO cover to transmission case. Tighten bolts.
5. Fill transmission with 4qts of transmission fluid. I have found that if you get a small funnel and attach a 6" piece of 5/8" heater hose to the bottom, it will allow for an easier time when adding the fluid.
6. Fill transmission until fluid is comming back out fill plug. Reinstall fill plug and you are done. It should take around 45min - 1hr to complete.
-Rich