UPgrade

I am using Winscp V5.5.1 and have several sites built but more importantly have many scripts that use winscp.com /script= and I want to make sure that if I upgrade to another version (like 5.7.3) that the sites and all my scripts will still work.

It should work.

Search the version history for "Change:" for (a few and minor) backwards-incompatible changes since 5.5.1
https://winscp.net/eng/docs/history
https://winscp.net/eng/docs/history_old