Do they sell a pre-built unit? I haven't seen one.
Anyway, we put one in with the hardware kit you buy from Lowes or Home Depot. The biggest thing to realize if you will have to take down the drywall on one side of closet to open it up for the framing. The framing would just be to take out a few studs and add a header. So if you can do framing, drywall, and a little finishing work, it shouldn't be that hard
Using the kit gives you the flexibility to use whatever door you would like (we used solid doors to match the other doors in the house).