I would not bother to pay someone to do this. If the tilt is small, why bother anyway?
I would do this the simple way. Pick a spot where you can insert a large crowbar/prybar underneath the edge of the slab, where you will wish to raise it. You may need to dig out a small amount of dirt there to get a firm grip.
In front of that spot, place a piece of wood to use as a point of leverage. It will also prevent the bar from sinking into the ground when you lift. The slab plus the air conditioning unit will be moderately heavy, so expect to need a long prybar to lift it. A friend may be of help here to help you to lift, as well as place a few well placed stones to support the slab after you have raised it to level.
One problem is the slab may crack if it is left without adequate support. To prevent this from happening, after you raise the slab to level, inject some expanding foam insulation into the void under your slab. This foam will expand to fill in that void, providing support for the slab. While you might think that simple foam would be unable to provide much support, remember that it dries to a stiff, hard consistency, and the load per square inch from that slab will not be massive.