Ah, Texan one owner 300D, a few ???s if I may?

[PiP]

I have been a lurker here for about a year, as I had a 240D a few years ago.

We just received my wife's grandfather's car.
1977 300D, one owner, 155K miles.

I am in Houston Tx, so howdy to all you Texans as well.

Preface this post with the fact that I have used the search button...

Anyway, there are three problems.

1) If you start the car and dont let it run for 10 minutes, the car wont turn off immediatly.
The car wont turn off unless the drivers door is locked.
I know the vacum system has some check valves, etc in it, but I want to know where the leak might be here?

I am going to buy a minivac, but when I get it, what do I do?

2 ACC doesnt work. It worked about a year ago, it would come on sometimes, and sometimes not.
I must have AC, Houston is about 6 miles from the face of the sun...

As well as not having AC,
This last winter, the only way the blower would blow heat was to put in on defrost...any theories?
Am I going to have to replace the selection panel?

3) The transmission was slipping and then catching at the 1-2 shift.
Now reverse is gone.
I want to stay with the Auto for originality.

Get it rebuilt in Houston, or should I buy a rebuilt one and install it?? How much are we talking? $1500?

I am up for all the advice you all can impart upon me with regards to checking the valves and other mechanicals as well.

Regards,
PiP