I was in the same situation having my own model railway but once I have used Trainz (TRS04 SP4) for the first time, I never ever used my model railway again.
Where else can one make one's own terrain, lay tracks, erect buildings/factories, build spur lines etc. and if one is not happy with some aspects, tear that part up and redo it in another way. :hehe:
Then drive around on it, either in outside view or on the controls like in real life and do railroading to one's heart content. All this without big money spending and doing real carpentry/plasterer/painter etc. work to build the scenery and tracks on your model railway.
Just for the price of one decent locomotive one can have several versions of TRS/TS in which to build as many different routes or download them with all the different other items available to use for your own created or d/loaded route.
Give me TRS/TS any time, I know where I will still be at it when I take my trip upstairs into the sky (or downwards as the case might be).
But I guess you knew this already as you are selling your model railway.
Cheers
VinnyBarb