Sorry for the late follow up on my topic of the same title two years ago. It took about 6-8 months to get the new sound board from Lionel as they were moving their service center, and then the next year was spend finding a college for my oldest son and getting him started (Trinity University in San Antonio TX, Business and Finance major, Baseball Player). The parts had to wait.
So this Christmas I retrieved my Legacy GP-7 and the received power board and sound board and installed them. The engine powered up and the sound works great!