Mike Brouse is in New Oxford, about an hour from YOrk, near Gettysburg. He is an independent tech now but was the MTH tech for years for Catoctin Mountain Trains and Hobbies in Thurmont, MD before the store closed last year.
I've had Mike do a lot of work for me. He is one of the most honest, qualified guys in the area. His prices are very reasonable and his work is second to none. Mike just did a total refurbishment on an MTH Railking F3 RTR set loco. I had him service it, do several minor repairs, gut it and install new Williams boards and electronics among many other things. It was a VERY long list that was not worth it to most people but it runs better than it ever did.
I'll send you an email to your profile with his contact info. I'd highly recommend you use Mike. You won't find a better guy in that region IMO.