You may be able to do the rebuild kit if it is less than 10 years old and you can find the local distributor of that brand of valve. Even then, they may have to order it in.
The easier way is to replace it. Most likely you have the 8" version, but if there is a question, pull it out and take it with you when you go to buy a new one. Don't use a torch, you will likely warp, weaken, and/or melt the PVC. Put a wrench on each side of the white teflon tape (looking from the valve, turn counter clockwise)...MAKE SURE YOU TURN THE WATER OFF FIRST. You are lucky it is in an exposed, unfinished area. If you are very lucky, there may be a shutoff valve somewhere in the area. If not, shut it off where it comes into the house or at the meter.
One other thing, look up local plumbing suppliers and go to one of them to get a new one. The ones you will find at Home Depot, Lowes, Sears Hardware, etc are a lower grade than the type plumbers use...usually not full bore either.
One last thing, buy a little roll of teflon tape and wrap it around the male threads before you thread the new spigot on. I know this is elementary, but if it's the first time you've worked with plumbing, worth a reminder.