Just do a little at a time. Maybe one night you do the spark plugs. Another night the front diff maybe txfer case and rear diff if you have time. Transmission drain and fill I do when I do my oil. I have 2 pans and do them at the same time. All the fluids are drain and fill, pretty easy. Even the coolant. There is no way I would pay someone $400-500 to do all that. The dealer even wanted to charge me $95 for a power steering fluid change. I did it in 15 minutes. The only special tool you need is a 14 Hex / Allen for the front diff fill plug. You will also need a 24 mm 6 point to do the rest of the plugs. It took me about 1 hour do to my diffs and txfer case all with AMSOIL and it cost me about $70 for the fluid.
My $.02 says that you do a little when you can, not all at once.
Oh, and I have my driveshaft lubed when I get my tires rotated and balanced.