To be blunt, you can research and answer those questions pretty easily yourself... But, in order of your questions, this will get you started:
Carpet can be found here:
Auto Carpet for Car, Truck, Van - Stock Interiors BTW, As has been said many times here, ACC carpet is the only vendor making molded carpet these days, so it comes down to picking a reseller. Get samples before ordering to match color.
Download a parts manual here:
Parts Manuals – MyMopar Figure out the part number and start doing some searches. You might hit a NOS part right away or you may have to spend some time searching for a good used piece. You will find one eventually with some diligence, but don't place a lot of weight in deciding to buy the car or not.
We have no idea what "heating system" is in the car. It could be a simple heater/defroster only or the run of the mill manual AC/heater/defroster. It's only when you get into the automatic systems that you run into problems. This involves first asking the seller about how it is equipped.
You can do all this research, but until you actually look at the car and get an idea of what it is going to sell for, you won't know much. Myself, I'm confused if it's the same seller from the first $2500 ad or if it's being flipped by another seller.
As
@Samplingman alluded to, you may find one of these in better shape for more moneyand you may be $$$ ahead not having to do repairs/restoration.