Don't know about tests. For ductwork and a replacement furnace, etc,
you want an HVAC contractor (heating ventilation air conditioning).

Do you have gas supply already, coming into the house ? If not then
that is the first thing to look into, since if you can't get NG then
you're sort of stuck.

I use a consumer ratings thing called angies list, it's a bit pricey
($45 a year or so) but it lets you look up ratings on companies that
do work on houses - plumbers, painters, hvac, you name it, also other
general services. The url is

http://www.angieslist.com/AngiesList...p?id=Baltimore

I get nothing from recommending them. You can look up things for your
friends and neighbors too.

You might also want to consider heat pump as Baltimore does not get
super cold like it does up here. Esp if you don't already have NG run
to the house.