6) Observe this INSTALL order
Install the three pre-requisite mods listed at the top.
Install the 2.5GB complete installation, and also the Master File (Morrowind_ob.esm) through the .exe installer
OPTIONAL: After that, install other updated Morroblivion files, including version upgrades, bugfixes, or patches (if any exist)
OPTIONAL: After that, install any other Morroblivion mods or components that you want to use, including the HGEC stuff linked above, the Morroblivion UI mods for DARNified UI, or any of the additional mods listed here.