I am in need of some direction on heating in my home!!

I have been having some issues with people giving me estimates on things and want some outside help to decide what to do!! I just bought an older house in PA, about 2100 sqft. Not all that well insulated which I am working on improving; duct work isn't well or at all insulated and the duct work in the crawl space (6" flexpipe ) seems to be crushed in some places.

I currently have a 11 year old Williamson oil furnace with a 1000 gal in-ground tank (not sure how old it is). I have been told by one company that the heat exchanger is cracked, but others have come and said it is fine.

I was thinking of replacing it (cost of oil being what it is) with either a gas furnace or an all electric unit with a heat pump. I live in a very rocky area, so I am assuming it would cost a lot to dig a trench for the gas line the 125 ft to the house. Getting an excavator to give me an estimate has been a joke. They have all said that they would let me know how much it would be once they dig it, find out what they run into and see how much time it takes. Un yeah, I'll just go in blindly - I have lots of money to throw around! I have gotten estimates for a :

Trane 2.5 ton, 30,000 BTUH all-electric heat pump system with the Trane variable-speed indoor air handler with 68,000 BTUH back-up electric heaters- $8,660.00

Carrier 2.5 ton 15 seer heat pump and Performance variable speed fan/coil unit - $9,935

Trane 4 ton xl 15i heat pump with hyperion xl variable speed air handler, media air cleaner, touch screen thermostat - $16,312 This company figured in replacing duct work in crawlspace to 7", increasing the amount of heat vents and cold air returns in the house, insulating the duct work. They were in the house for 4 hours whereas everyone else was there for 20-30 minutes and seemed to just go with the size of the old units. And it seems to me that if the duct work and vents arent adequate, then the furnace isnt really working efficiently anyway.

I think my questions are: should I go with getting a gas line installed for a gas furnace and heat pump?

Get an electric furnace and spend the extra money fixing the insulation and duct work?

who is right on the ton size furnace I need for 2100 sqft?

should I just stick with the oil furnace I have and add on a heat pump?

AHH! This is so confusing - if anyone can help I'd greatly appreciate it!!