I really hope you are prepared for a 6 foot lizard. There are thousands of these animals in rescues all over the world because people don't realize what they are getting into when they buy that cute little baby in the pet shop. I wish you hadn't supported the import trade by purchasing one of these, but instead had gone to a rescue where there are hundreds that need homes.

Get the heat rock OUT... Regardless of if it is on a thermostat or not, lizards cannot sense heat on their bellies and will burn themselves. They should be heated from above by heat lamps as well as good UVB lights. The ReptiSun 10.0 is a fairly good fluorescent bulb, even the 5.0 is OK(do not get ESU bulbs or the compact fluorescents), but a Mercury Vapor Bulb would be your best bet(cost is around $40-$50). Iguanas need high humidity, a varied, well-supplemented, vegetarian diet, and massive amounts of UVB. They are not cheap to care for in the least.

As for the housing, I would keep him on paper towels until you can get a fecal sample into the vet. It will be easier to keep track of the consistency, rather than having to dig through the nasty repti-bark for it. If you want to use bark, try Cypress mulch. The pieces are larger and therefore can't be swallowed, which in turn can cause an impaction. The Cypress can be found at Home Depot/Lowe's in the garden center for about $3 a huge bag. Bake it beforehand because of the risk of external parasites, and also because it can be quite wet when you buy it. I put it on cookie sheets, spread it out, and then bake at about 250 until it is dry. Usually takes a good couple of hours.

Go to WalMart as well and get another digital thermometer w/hygrometer. Iguana husbandry can be very specific, and if their temperatures/humidity aren't just so, then they won't do well.

Get a large, flat rock, and use that for the basking area. Direct the heat lamp onto it and measure the temps on the rock surface with the thermometer probe. Should be around 105-110 degrees. The cool side should be around 80. Humidity needs to be in the 70-80% range. Mist him a few times a day so he will drink and be hydrated, mist his greens and veggies so as to get extra water into him. The UVB light should span the entire enclosure, not just in the basking area. So a 4' cage needs a 4' light, or a MVB bulb.

Their care is fairly similar to Bearded Dragons, except for the humidity part and the diet.

IMHO, I think a Bearded Dragon would have been a MUCH more suitable pet as they stay smaller, are more interactive and personable, and won't try to eat your lunch when you try to pick them up(or break one of your fingers when they tail whip you). I hope you get his husbandry all straightened out, and good luck with him.