A few questions though:

1) Is it even possible?
2) How much should it cost me?
3) How can I go about doing this?

My Wife is very petite and she has a difficult time getting into the car. This is an option I'd like to explore.

TIA

i'm sure it's possible.

the cost would depend on which brand you choose, and maybe the type: running board, tubular step, etc.

http://www.diynetwork.com/diy/ab_parts_accessories/article/0,2021,DIY_13690_2271311,00.html

when searching, keep in mind that the Mercury Mariner, and the Ford Escape, are the same vehicle.

http://www.suspensionconnection.com/cgi-bin/suscon/scan/fi=products/st=db/co=1/sf=category/se=Nerf%20Bars/op=eq/nu=0/sf=veh_make/se=Ford/op=eq/nu=0/sf=model/se=Escape/op=eq/nu=0/ml=25/tf=category/to=x/tf=veh_make/to=x/tf=model/to=x/tf=description/to=r.html

http://www.runningboardwarehouse.com/index.asp?PageAction=VIEWCATS&Category=382

Cool man, thanks a whole lot!