When you know how to do it changing the fork seals will take about an hour. If all you are doing is changing the seal then it can be real easy. If you want to disassemble the entire fork tube there can be a trick or two that can be a bitch.
It took me a few days to figure out how to do it. I am not familiar with your bike but my Yamaha YZ had an "inverse" nut on the bottom and I had to make a tool and then improvise an impact wrench.
If you are not ready to tear into the forks you should at least top off the oil. On my bike it is a simple matter of releasing any pressure, unscrewing the top cap (careful, it can be spring loaded), pouring in the proper amount of oil and then replacing the cap. The only trick is knowing what the proper oil level is, so get a manual if you don't have one already.
Topping off the oil should restore proper shock operation until a significant amount leaks out again. If it doesn't, then just replacing the seal won't help, you will need to rebuild the inner parts.
Rod