If the mechanic did check the level via the dipstick he would have checked it after filling it and a few minutes after shutting the engine down, so find a nice flat area and do the same, (on the earlier models that is how GM say to check the level in the handbook, so I assume the VE would be the same). With my VX SS if I check it shortly after turning the engine off the level is usually right on the full mark, if I leave it parked in the garage overnight and check it the next morning, the level is a good 5 to 6 mm above full, the oil drains down from the overhead areas overnight and reads higher. I usually check mine after it sits overnight but I know it will be a bit over the full line. I would check your handbook and see what the recommended checking procedure is and if they say to check a few minutes after shutdown and it is only a little over the full line I would not worry about it.
