1. Carefully clean the disk.
2. No such replacements exist.
3. There is no online version to download from MS.
4. You could start over and purchase the Steam version at full price.
Not being a smart a## but you install them the same way as for the MS version of FSX. It's just the paths to the folders are going to be different, and most planes have a Read-Me for directions.
Mac,
Move your cloud graphics to Ultra instead of low and then see how they look. Also, the graphics for clouds are not the same as in past versions, so REX nor anyone else can't do anything yet.
Click on the link.
Go halfway down the page.
Click on the big green bar that reads Download 2.0
Unzip the contents of the download into your Community folder in MSFS.
You may need a FREE Flightsim.to account in order to download.