if you have a dc powered truck (4 power cables to the drive motor), it may be as simple swapping 2 cables, but getting a model and serial number is very important for us to be able to give you the correct information.
When (not if) someone gets hurt from untrained people working on and driving the machine, your employer will be very bothered by the fines the government hits them with. Pallet trucks require operator training that includes instruction to not work on the machine unless properly trained, as per USC 1910.178 (the OSHA regulation that covers powered industrial truck operator training).