Wait! Seriously?? Oh my God, take it to an experienced independent watch-maker who actually knows what the hell he's doing. I learned very early on as a watch enthusiast that a watch that seems to run perfectly fine is a horrendously poor indicator of what's going on inside of it. Gears could be grinding against each other, getting very slowly destroyed. Or oils inside the watch could be turning to sludge. Meanwhile, on the outside, the watch keeps perfect time.Here is my Grandfather's old railroad watch that I inherited from my Dad. I took it to a local watch dealer / repairman recently to see if it needed cleaned or lubed. He said it's running fine, and that I shouldn't mess with it at this point....
More than likely he gave you that utterly ridiculous excuse because he lacks the skills to work on that particular watch, but his Pride wouldn't allow him to be honest with you.