It's not a hard job, just a little tedious.
Many will say you can use a hand stapler(like a Stanley) but I find them useless for a good job.
I use a Craftsman air staple gun.
Put the foam in place, put the cover on. Most will have a small pocket for the front to fit in. Pull the back as tight as you can and put a couple of staples in to hold it there.
Put a couple in on the front. I like to them work from front to middle then back to middle, pulling the sides tight and even about every 2 inches and placing a staple on both sides to hold it. You may find that when you get to the middle you may have to fold the excess into a crease. Just staple a couple times right over the crease on both sides.
Now go back and pull things taught again and place a staple in between your first staples.
Usually it will look kinda sloppy untill you are nearly done, but things seems to shape up towards the last few staples.
If your cover is a thick vinal, you will find that warming each area up with a hair dryer makes things work nicely.
Take a look at a stock seat job to see where the best place for the staples are.
Try not to have too much air pressure on your stapler, as it will tend to slam the staple all the way through the cover.
Don't be afraid to put too many staples in.
Good luck.
$12 bucks for a pro job aint bad. Tell them you want it nice and tight.