I was quoted $3300for an installation of a new ac trane XB13 OR $4200 FOR FURNACE XR-80 AND AC BX13,I was wondering if it's a fair price or should I look a more quotes ,I live in New Jersey thanks

They sound reasonable to me just in general, but many people like to get 2 or 3 quotes.
Quotes may vary by how depressed the economy is near you, and what kind of home and basement and other plumbing and size of old one and access and how much adjustment to retrofitting will be needed and so on.
I'd be just as interested in how long they've been in business, the grade of the people doing the work, journeyman, apprentice, etc. how thorough the contract looks, removal explained, care taken of tracking mess through the house, when they want their deposit, and what their guarantee is for day of installation (not too much concern at this time of year), plus their guarantee of work, and finally, how reachable they are at all hours.

I think you have a good quote on this price. Make sure that the inside unit is installed where you can pressure wash the cooling coils without water damage. It should be in a garage or room with a floor drain. DrTom4444

The main problem could be the size of the duct work, especially the return duct size and the size and number of returns. You want the return grill to be at least two times the footprint of the unit. For example, if the end where the air enters the air handler is 20x20 you want at least two 20x20 return grills with filters or a bigger return. The bigger the return the better pleated filter can be installed without losing airflow and efficiency. Duct size and returns affect your cost of operation more than any other factor. Also, never install an air handler in an attic because it will use 75% more power to cool. DrTom4444