In order to keep your Guild Hall as-is, so it doesn't poof on you, you have to pay the Escrow. Or at least ensure you have enough funds in your Escrow account to keep it going.
To pay the Escrow, from inside the Guild Hall, click the default door (not the wooden door) to get to the Guild Hall front yard. Near the (NE?) corner of the yard, there is a stone kiosk. Standing in your yard, click the kiosk. If you're not standing in your yard, you won't be able to manage it.
On the kiosk window, click the manage button. This brings up the Real Estate Management window. At the top right corner, it shows you how much time you have remaining in your Escrow account. You'll want this to be many many years in the future. People forget. Just sayin. The Default Upkeep field allows you to choose your preferred currency. Use the dropdown to select the currency. In the kiosk window, the Upkeep field tells you how much it costs per week in your preferred currency.
To add money to escrow, choose your preferred currency and click the Add Week (or Add Day) button. If you plan on adding a lot of money to Escrow, you will need to press that button A LOT. On my Guild Hall, I set the time left to 1000 weeks, so I was clicking for about 10 minutes.
When you're finished, close both windows and click on the front door of your Guild Hall to get back in.
Hope that helps.
Dru