Abcdeflijus wrote on Aug 2^nd, 2021 at 3:36am:

Just wandering if it will remove all my liveries?

It will overwrite the aircraft.cfg so that they won't be visible/selectable in the sim, but the texture.xxx files will remain, and so do the downloaded zip files.

To re-add them:
Open the 737 classic ACE, select the model (-300, -400, or -500 in LOCAL mode), then click on ADD, navigate to the P3D\Captain_Sim\737-classic\ace\zip folder select the livery and click on OPEN. This will add it to the aircraft.cfg.
You will need to do this for each livery you have added to the 737 Classic.