> It appears the Yuri's Revenge MISSIONSMD.PKT file must be loose in the RA2 directory? If so how do I use XCC Mod Creator to create this file on mod launch?

You could abuse the video category or update your XMC/L.

> (Sorry if this question has been answered before, but the 'Search' option appears not to take you to the thread, but to the individual post.

You can go 'up'.

> Also I have no idea how to access older pages.

Increase the first value in your preferences.

This forum is very confusing...)

True, sometimes.