I have commited on a replacement of my old Trane HP and air handler. New equipment same size as old higher seer.

Carrier HPA442 3.5 ton 14 Seer
FX4CNF048 air handler

None of the HVAC contractors I contacted (4 - 2 carrier and 2 Trane)do any of the load calcutations that you guys talk about so I went with the same size. It has taken about 3 months to finally get the bids made, guess they are busy or don't need the business
The one I chose is about 60 miles away,just didn't like the one local and he was several hundred higher.You pay a bumch after warrenty period expires,100+ a mile both ways.

Would appreciate any advise on things to watch for in the installation process.
Ducts and vents are metal and well insulated
Lines will be replaced.
New metal plenum and distrubution box
What else??

Are there any rebates on this equipment, I was not told of any.
Thanks
Fred