What type of contractor would I hire to level a concrete floor?
I feel that you should dive a bit deeper and resolve the root cause of your problem. 2" of subsidence seems to indicate a bit more work than simply using a self leveling material, you have support/foundation problems. Consult a professional foundation remediation contractor to see if you can get an idea of what the cause is. I would hate to see you "level" it only to have it rise or subside again, undoing your work and money.