Definitely a DIY. I just replaced the passenger side a few weeks ago and I did not remove the plastic liner. There is a little door right beneath the light assembly (for changing bulbs) you can get you hand into and then I used a socket on the end of a short screwdriver to remove the three retaining screws for the whole light assembly (one on each side and one on the top - to get at the one on the top I removed the back of the assembly as if I were changing the bulb then you can see it). Once the assembly is loose you can pop off the lens and work the lens out of the opening, work the new lens in and then reassemble. I could not get the whole assembly out as it wouldn't fit. Having said all this, it might be easier to remove the plastic wheel liner since you need to jack the car up anyway to get under it! Maybe you could remove some of the screws up front and just pull it down enough to get access.