On the boat towing issue....you may want to think about your boat before you buy the tow vehicle. We've owned a boat for 8 years and have used several different tow vehicles for it.
Here's some info on my experience....YMMV
We have an 18-Foot Searay, with the 4-cyclinder I/O motor. It just barely gets in under the 3000lb limit here in Florida for a boat/trailer combo that doesn't need trailer brakes. We used Ford Explorer's to tow it with (5000lb towing capacity, 6 cycl engine just like the Xterra) and it was ok...on flat ground. Kind of exciting if you had to make a quick stop. Towing in hills was a drag (Florida barely has hills compared with TN)...trying to stop coming down hill was more exciting than my wife liked...
The last trip of several hundred miles to the west coast (of FL) cooked the Explorer tranny. We needed a new tow vehicle.
I bought a Ford F-150 4WD pickup with the 5.4L V8, auto transmission. Surprisingly, gas mileage is only reduced from about 18-20mpg with the Explorer to about 14-16 with the truck (around town).
We also sometimes launch the boat at less than perfect boat ramps. The 2-wheel drive Explorer would often get stuck or spin the tires, even on concret ramps. Particularly if the ramp was steep and wet. I always carried a shovel. It's no problem with truck. With the beefier motor (more torque) and more aggressive tires, I haven't even had to use 4WD.
Genral towing is much improved too. I barely know it's back there. It goes, we don't have to worry about getting stuck, the truck sits up higher so I can back clear into the lake if I need to (I regularly submerged both the bumper and tailpipe on the Explorer) and the truck stays high and dry. Mostly importantly, when I need to stop, it STOPS! Being able to stop safely is easily the single biggest improvement in our towing situation.
Buying the tow vehicle first will limit your boat choices and you may find that you'll want a bigger boat than your tow vehicle can safely handle. Although the Xterra is rated at 5000lb towing capacity (the new ones, older ones are 3500) that is the max and not necessarily what you will feel safe towing.
Like most boat owners, I wish my boat was 2 feet bigger (and had 2 more cylinders)...maybe some day!
Cheers,
Joe
Also, tell the Mrs to get better, darn it! If she is still crutching around and can put some pressure on her knee, here's a gizmo that she might find useful. I used it for about a month, post foot surgery. It's called a "Roll-About" and I rented it from the local medical rental shop.