Well, I'm still trying to figure out my 75 gallon tank lol, so I'll help with as much as I can.
First, what type of thermometer is it? Does it have a humidity guage also? A larger cage causes the humidity to drop, which can cause health problems, just as too high of a humidity can.
The basking spot (heat light) should be on the "basking side". You should have a cool side, also (you probably know this). With my 75 gallon, I do have to occasionally use two lights to get the cool side up to the "correct temp", but I don't think you'll have that problem with a 55 gallon and a 100 watt bulb (I use Halogen bulbs and I'm thinking that a 100 watt bulb may cause your temps to get too high). If I'm right about that (not sure lol), you can buy a stand to hang the light fixture up higher or a dimmer fixture work great too (that's what I use on the cool side, when the temp drops around here). Did you get two fixtures so you had one for the basking light and a ceramic heater? Sorry, I'm just curious. The UVB (glad you're getting the ReptiSun 10.0 tube

) should stretch the length of the cage (which it sounds like you already know) and should be placed side-by-side to the basking light, so when he/she basks, he/she gets the proper UVB rays. Your beardie needs to be able to get within 6-8" close to the UVB...too far away doesn't benefit your beardie and too close causes eye problems. I recommend reptilesupply.com (this is where I usually get my supplies, but I have had a few mis-communications with them, causing a delay in them shipping my things...I would still recommend them though...great prices), petmountain.com, bigappleherp.com, for the UVB. Don't buy one from a pet store...they rip you off. In the future you can just use a regular house hold bulb or Halogen bulb for basking, they're a bit cheaper and work just the same. As for a fixture for the UVB, I'm having trouble finding one for a 36" bulb (I am using under the cabinet light fixtures right now, you can buy them at Walmart for about $7...they are for the 18" tube lights, though). I don't know how long a 55gallon is...but I wouldn't recommend getting a 36" bulb. They aren't that common. Hoods are pretty expensive. I have a 30 gallon (36" long) tank, also, and use two of the under the cabinet light fixtures with two 18" ReptiSun 10.0 bulbs.
Oh, and I have had a few problems with my bulbs getting a little too hot and too close to the edge of my tanks...they can "melt" them. I'm not sure if they'll melt the screen, because I use stands...just something to watch for.
Hope that helped some...I tend to ramble and it's little late/early lol.
Abi