it will work. all you have to do is unpin the forks and disconnect the hoses to swap.
however, most of those wallboard loaders are designed for power and finesse, not speed. you may find that its way too slow for what you want to do. the cranes designed for handling logs can be run with plenty of finesse for reaching in yards, around structures etc. but will have the speed to get unloaded in a hurry back at the yard. (by finesse, i mean that i picked up an egg off the top of a mountain dew bottle, cap off, and set it on another)
a new grapple will run you 5-10k. for that you can get a good used log loader.