My 40+ year old Hydrotherm gas steam boiler in NJ ran dry and ended up cracking.

I've been getting quotes the past couple days, but need to make a decision ASAP, as I've been without heat aside from electric space heaters.

What brand boilers should I ask contractors for? Is there much of a difference?
What should I be asking contractors?
What are good warranty lengths?
Anything I should keep in mind?
Does pricing depend on the boiler I go with, or will it mostly be labor?
(I've been offered lennox, kenmore, peerless so far)

Are there any government/state rebates I can take advantage of?