I don't know if you searched for it or not...but this is a fairly common question.
Anyway, there are many people who have put SRT8 'rails' on a regular WK. From what I understand, its basically unbolt/bolt-on. If you want to remove just the cross-bars, you have to pull out the little silver pin on the bottom of the knobs. If you can't do that, you have to remove the caps at the end of the rail so you can slide the bars off.
FYI...a good place online to buy a lot of Jeep parts/accessories is justforjeeps.com
, a lot of people (including myself) have purchased from there. Also, check out wkjeeps.com
for a lot of other useful info.