Yes, they do need uvb light, very important.
As far as a 20 gallon could be for one, but 30 is better and always remember, BIGGER the tank the BETTER !
If you handle your new friend, they become very friendly and tame, but they like to take sudden leaps, LOL so just keep him safe, I like to play with and handle mine while sitting on the floor. They will jump right into your hand when tame.
Rather than me typing alot of info here are 2 very good sites, to read when you have time. One is Will Wells site, a forum buddy. Lots of good pics and a CAPTIVE CARE sheet. The other site is also full of good info in my opinion, here they are
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http://www.mountainboomer.com/crotaphytus/
www.collaredlizards.com
Hope they provide ya with all the info your looking for, You will love a collared, more active than beardies, I love my beardie, but collareds provide more entertainment, 
Anything else, just ask, someone here will TRY their best to answer you have a good one, 
Eve
