Your plan sounded good until you got the part where you said that if it is leaking that you would evacuate and drive it for the weekend.

Evacuating a leaking system and leaving the vacuum beyond a short time for leak detection reasons is a BAD plan. The vacuum will draw in outside air which contains moisture. The oil will absorb the moisture. Depending upon the particular oil, when moisturized it can create a terrible acid.

If you do have to drive away without the problem fixed, have them draw a vacuum then put in a leak charge. This will make a positive pressure and eliminate the possibility of moisture introduction.