The only step I can think of is to be sure you get everything positioned like you want it (side shifter centered, push/pull drawn all the way in toward carriage). Then while you sit in the seat with key switch on, but engine not running..........operate both the side shift function lever and the push/pull function lever several times, operating the levers fully in both directions. This will allow any "pent up" residual pressure in the cylinders of both devices to bleed off internally back to the truck hydraulic tank.
Then turn off the key when you get that done.
But you are still going to lose a little oil from the hoses.
Make sure you mark all the hoses that have to be removed so you don't have to do a bunch of tracing later if something gets mixed up.