As mentioned above, many of us have used any brand Mercon or Dextron tranny fluid per manufacturers recommendation. Some RV's come with clear hydraulic fluid in the reservoir ... the tranny fluid mixes just fine. You're looking for a low viscosity, low foaming fluid.
The reference to fork oil is in case your jacks pop while sitting on site. The Torco fork oil or Caterpillar oil additive recommended by Lippert is
added in place of a couple of quarts already in your system. It addresses the "stiction" issue.
http://www.lci1.com/images/support/lipsheet/0295.pdf