I had taken my unit into Camping World as the slide was not completing a seal on the lower front and was out by 1-2 inches. After aligning the slide the tech turned a couple of nuts under the slide to fine tune the amount it came in. They said bolts on the slide rail were loose allowing the slide to get misaligned. It was taken care of under the Forest River warranty.
Personally, I would take your unit to another RV service center to get a second opinion and price. After seeing the tech mess around with mine, I most likely would not attempt the adjustment myself.
Best of luck!