I believe on your coach that the panel surrounding the tire lifts up. If there's a hinge along the top edge look for pins / screws somewhere on the lower left and right of the fender (may be covered with round trim pieces).
Otherwise - a call to WBGO may help ...
2015 Itasca Ellipse QD | 2014 Jeep Grand Cherokee
Here is a thread on an 03 Ultimate which is also accurate for my 04 Vectra and I believe the 05s, so might point you in the right direction. Has info on removing light (prior poster is correct, need to remove screws holding fender and hinges up) and also has info on bulb replacements.