dose anyone know where I can find a track layout for the old Wellington area?
I’m unaware of one online, but there’s a map showing trackwork and structures at Wellington/Tye as of 1909 on p. 185 in Charles and Dorothy Wood’s The Great Northern Railway (PFM).
There is a beautiful track diagram of Wellington Yard and Cascade Tunnel Station Yard in Charles R. Wood’s book “Great Northern-Lines West” reprinted in 1997 by Signature Press. These appear on page 117 of the book and are quite detailed.