Hello Allen;
Yes that pretty much sums it up. A couple of things to be sure is;
1) Make sure the box you mount it in is adequate size to house your contractor, possibly 8"x8"x6"
2) Make sure the pressure switch is kept in the circuit
3) Be sure to bond or ground the box and maintain the bond to the compressor.
Some compressors will have a magnetic starter on them but will more then likely have a 240 volt coil. Be sure if you buy a contractor that it has a 110-120 volt coil and the current rating is sufficient. Also check the horse power rating on the contractor to be sure it will handle the compressor. There are lighting contractors that will not handle the surge of the motor.
Here is a crude sketch of what we are discussing,
http://s1142.photobucket.com/user/52_Ton/media/IMG_1785.jpg.html?sort=3&o=0Mark
