Well the vacuum leaks and transmission issues could very well be related. A\C is not usually a "hard fix per say, just usually expensive.

If the rust doesn't concern you, then it doesn't sound too bad. You have a car and know the entire history of it, that's huge. Honestly, these cars don't mind sitting nearly as much as you would think. The only real issue will be stuck brakes from sitting. The rest is probably fine. I say go for it.

$1000 and your labor will probably fix everything but the A\C and get you a good running car.

__________________
2004 F150 4.6L -My Daily
2007 Volvo XC70 -Wife's Daily
1998 Ford F150 -Rear ended
1989 J-spec 420SEL -passed onto its new keeper
1982 BMW 733i -fixed and traded for the 420SEL
2003 Volvo V70 5 Speed -scrapped
1997 E290 Turbo Diesel Wagon -traded for above
1992 BMW 525i -traded in
1990 Silver 300TE -hated the M103
1985 Grey 380SE Diesel Conversion, 2.47 rear end, ABS -Sold, really should have kept this one
1979 Silver 300D "The Silver Slug" -Sold