I sent you an e-mail re: manuals. I will need your address since AOL has a limit on how much can be sent as an attachment.
You indicated that you were getting the Excella on Saturday. Did you? We love our '78.
The F-150 should do it ok, check the towing capacity. I found this information on the web about the 2003 F-150.
The towing capacity is affected by the rearend drive ratio.
The Windstar has a maximum towing capacity of 3500 lbs. That is not enough for a 7000 lb trailer.
As for things to look out for on the '78 Excella. It is strictly a matter of how it has been maintained over the past 25 years.
Axles: It has Henschen axles. Search on Henschen on this site for lots of info on them. There is an easy way to check if they are wearing out.
Tires: Depending on age, they may need to be replaced. Replacements are Goodyear Marathons Load Range D. I think the size is 225/75R15 Again do a search,
Wheels, brakes: The trailer may have the original Vacuum braking system or it may be converted to electric. Have them checked. I had my electric brakes rebuilt just to be safe.
If it has a rear bath, there may be a problem with sagging rear-end. It is not an issue on the rear bedroom.
The rest, appliances, interior furnishing etc... are a matter of maintenance.
Airconditioner: Probably has the original Armstrong. If it goes bad, I am told it cannot be fixed since there are no replacement parts. The replacement is the Dometic Penguin 13,500btu. That needs an adapter from the Airstream factory to mate the Dometic to the curved roof of the trailer.
When I got mine, everything worked and the only appliance I have had to replace is the A/C. Unless you are planning to come south, you may not need and A/C anyway.
There is a lot more to think about but by checking this website and searching for stuff or just asking questions, you will get tons of help.
Welcome to our world. You will find that Airstreamers are a breed apart, and that the Airstream is not just another trailer. The '78 qualifies as "Vintage" so check out the Vintage Airstream Club.
carries parts for the Airstream. It's owner is a regular contributor to the forum. You can trust his opinion without reservation. He has been in the Airstream business for a long time.
That is enough for now. Don't want you drinking from a firehose.