Need help trying to find a replacment gas heater

We are trying to buy a house, and we think we have found one, but the gas burner is over 40 years old, and we want to upgrade to a more efficent gas unit (one that does not require a chimney). How can I find a good deal on an installation & maybe a contract with a company? I have gas in my apartment now, but my landlord does all the work with them. Does it work like oil where if you sign with a company they give you a new boiler cheap?
Help please

anyone?

I would first research gas water heaters. I used to work for a rep company that repped manufacturers of water heaters and such, so I could FM you the companys phone # or I could have my friend mail you some info from the literature dept.

We just got a new oil burner installed. I don't know if it is the same with gas burners but I am assuming it is since the compnay we used installs gas burners also. We signed a contract with them for oil and we got a free service contract with the purchase of the new oil burner. The burner itself was very expensive. We got a new water heater also and all together it was $5500. My father used to own his own heating compnay so I know a lot of people in the industry. Even if we got a new one at cost it would have been over $3K for this model. So I didn't think $5500 was that unreasoable considering labor for 3 men x 7 hours and the service contract.
Good Luck.