Hey mate there was a really good post on this subject some time ago so try a search..
If unlucky with that,
Go to bunnings and get a 25mm roller,they are originally for sliding doors I believe,the one your after has green cardboard insert and is in a glad type resealable bag..It comes with the roller and a nylon lock nut..Hope that describes it for you..After you get it take the back windows out you should be able to manouver the regulator to pop out the top exposing the two metal pins the old shitty rollers used to be attached to.When they are out far enough from the window get an angle grinder and cut the fokkers off. After you have done this just push the remaining bit of pin through,you may need a punch,this will leave a perfect hole as the pins were originally just pressed into the regulator.Get your new roller ad attach,I didnt use the nylon nut as i just couldnt do it up without the roller spinning aswell so I just used a normal nut and spring washer..i think from memory all i needed to undoo on the regulator was the 4 bolts around the winder to get it up to enough to work on,mind you I hadnt sprayed the car at that stage so using and angle grinder near the shitty interior/body didnt worry me soo much,so you may want to take the whole thing out if you do just dont move the channeling in any way to save time on having to adjust the whole thing again..The end result is worth the time as they are just a dream to use after with no play..