I have done this twice (one each side). The cross nut can be difficult. The first time I mangled it. The second time I bought a vise-grip style chain tool, and it was sooo much easier.

See http://www.toolup.com/productinfo.asp?id=20R&Manuf=IRWIN+Vise-Grip&Page=1
for a picture, I bought a cheap one at Northern Tool for about $8.

I would be interested to know how much the "real" tool costs. Of course the previous caveats about torque apply.

In retrospect, I would have done both sides at once, since you need to align the car afterwards. Depends on the age of the car and reason for repair.