Liquidating Entire Layout

You may want to try Trainz. I've dealt with Scott Griggs and he is a reputable person.

Another auction site, Pittsburgh area, they will go most anywhere.   Expect after all expenses, may be 15%,  or less of purchase price.   The Fort Pitt Highrailers worked with this auction site, to help disperse Matt Irwin's (large) collection.    

My suggestion would be that you start dismantling the layout asap.  If you haven't started yet, box and inventory all of the stuff that you want to sell.  Pull up all the track, switches, bumpers and anything else that can be resold and inventory them for sale.  From my old layout I even sold a bunch of terminal strips in a single lot.  The layout itself will end up in the trash.  Don't procrastinate on taking the layout down.  Based on my own experience, you are looking at a least of couple of full days (or possibly more) to do this.

With an inventory in hand, you can then then communicate with potential lot buyers to see what they might offer and auction houses to see what they think the items might bring at auction.

When I took my old layout down, I had the time and the storage space to sell what I wanted to sell by myself.  I sold all my track, switches, bumpers, turn-table powering kit and unused spools of wire, here on the For Sale sub-forum.  I sold several engines and freight cars here as well and locally through Craigslist and Letgo (free phone sales app).

You may also want to decide if you want to keep any of your current trains.  Even if you can't have a permanent layout, maybe a carpet layout is a possibility?

Jim