You should always turn your rotors when replacing your pads for maximum braking efficiency.
In fact on many large trucks, they will even grind the pads to ensure a good fit.
Even new rotors should be turned to verify a true surface.
When your dealing with the weight of any large vehicle, brakes and/or braking systems should not be the place where you may want to save some money.
Can your wheel bearings be repacked vs. being replaced ?
Also remember that everything posted on these forums are opinions and not necessarily correct.
Use due diligence when using the information given. Ask me how I know this!
Good luck.