Using Addons with existing homemade campaigns (D&D 5E)

I created a large campaign from scratch that took my players from level 4 to 10.  Our game includes a ton of maps, images, and sheets. To take the next step (and since I don't have as much time), I purchased Tales from the Yawning Portal.  This was partially because it was advertised as "All Access Vault Enabled."  When I tried to import characters exported from our custom campaign/game into the game with the Tales Addon, I was unable to do it at all (says its a limited use vault game).  I've reached out to tech support, but wanted to know: Are there potential problems with adding on a Tale from the Yawning Portal right into our current game?  Are there concerns about file sizes or number of characters/sheets/images in a single game?  If I absolutely have to (and it doesn't break stuff), I can simply add in one of the addons into our existing game. Ideally we can import into a fresh game, but I appreciate your thoughts on possible problems with adding an add-on to a homemade campaign/game. Thanks! Matt

It should be fine to import to your existing game. You should make two copies of your existing game if you're worried. Leave one copy unchanged as a back up in case things go wrong down the line. In the second copy, try adding the Addon and make sure nothing goes wrong, then you can add it to your real game.  After a while of playing, when you're sure things are fine, you can get rid of the copies.

Don't know why I didn't think to simply make a copy to be safe.  Thanks!