Ryan told me the rear ones are harder to get at, but just take your time, and don't cuss much, they will go in. :).
I had one of the wheel wells out for some lights I mounted that I could turn on while running in "cattle shoots" at night in construction sites (jeeps call them rock lights I think).
the idea was to lite up the road just outside the dually wheel wells so I could see the wall. Lights were high enough so they would not bothering drivers that are next to, or behind me. The wheel wells were not that hard to get out. I ended up moving my lights so I had the wheel wells out 2x's