2000 Roush Mustang

2000 Roush Mustang, 78.8k miles, v6 3.8L.

Problems:

1. The power locks started acting weird a couple of months ago. They would maybe unlock the first time you hit the button, but if u continued to hit it, they would slowly "lose power" and move less and less each time until they would stop moving. Now, they hardly ever work. From what I have read, I think it might be a vacuum problem, but I don't know how to check it or how to find the leak if there is one.

2. The a/c and heat has not worked right since I got the car. It blows perfectly cold or hot, but it will only blow out the top vents or the floor vents. If I set it to floor, it still shuts off the top vents and vice versa, but it will never blow out the front vents.

3. One of the top left air vents on the dash is broken in half. It's a little oval plastic vent that is only a couple of inches wide. I have looked online and cannot find where to order a replacement. I tried looking for "air vent" and "dash vent".

Any help you can offer would be greatly appreciated. Thank you.