The tranny in these is the 4R55E (not the greatest, but a damn sight better than the A4LD). Agree, check the maint records. Also, run the VIN thru CarFax, unless you know the guy and the history. The only unexpected prob I have had in 2 years is the serp belt tensioner fell, yes fell, off. Oh, yeah the AC compressor went out a year ago and I short belted it, it still is. But AC on all Fords SUCK ! Run the AC thru its paces and observe, listen for potential problems, If the AC goes, it is not cheap (my estimates range from $800-1300). And make sure the recall for the sway bar links has been done, but if it hasn't, I suggest ordering the set from Jegs, for 1/4 the price and a MUCH sturdier set.
If you decide on getting it, with 41K you can then proceed to do the mods people have listed here, and replace all fluids with syns.
Mine has been a good runner and fairly dependable.