Highly recommended contractor installed a 3-1/2 ton, 14 SEER, Rheem HVAC system in my home today. They did not replace the very old, slightly damaged, concrete slab to mount the new condenser or clean the existing duct work. The return air duct is very dusty. I feel I got a great deal at $3,750.00, but shouldn't they have replaced the slab and duct when replacing an old (15 year) system? I assumed this would be done as standard. I should have got everything in writing, but obviously did not. Just curious as to what I should have expected realistically.