If Randy helps it shouldn't take long at all. The thing is I'd want you to do a few; so next time if we aren't available you would feel comfortable doing them alone.
Last time I did my plugs it took me 10-15 minutes. It was only that quick because I had the blower out of the way. I think Randy has done his a few times, so I'm sure he is proficient at it. So depending on how quickly you learn plan on a couple hours to be on the safe side.
Go ahead and get the plugs, and gap them to what ever you want so that will be out of the way.
You can bring the truck to my house, I should have all the tools we need, and if I don't I'll buy what we need.
-Mike