Air Tools and Impact Wrenches, Need more specifics Options

[Celicav]

I've read posts on installing your own lowering springs and how much help it is to have air impact wrenches or, esp. when dealing with that nasty sway bar bolt in the rear. Basically, I am looking for wrench that I can use to take the lug nuts off the wheels and that can handle any bolts that I have to deal with when installing my own springs. What are the key specs I should look for (minimum Torque, drive size, RPM, etc)? Also, are there cordless, non-air impact wrenches that will work? Where is the best place to rent these items? Like Northern Tool or auto parts store? Thanks