How to recruit Shareel

Concerning the TR_XXX.esm, you're most likely trying to use Tamriel Rebuilt (good choice!) Antediluvian Secrets, which requires Map 1 (Telvannis) as well, so I guess the latter has been forgotten.

Concerning the warning, this means that one of the plugins you are using was saved using a different version of the game main files, e.g. native Morrowind.esm while you're using the Morrowind Patch Project. You can usually ignore this, although you should at least once check whether you're accidentally using a Morrowind-without-Bloodmoon version of a plugin that also has a Morrowind-with-Bloodmoon version if you have Bloodmoon installed or vice vers.

If you want to get rid of the warning for good, you have to open the respective plugin's .esp file with the TES Construction Set (using your actual Morrowind.esm etc versions as base files) and simply save it again (keep a backup though). That should update the claimed dependency without modifying anything else.

According to this page, there is no "questline" of any sort included in this mod.

As for the dungeon :

SECRET CRYPT is just a regular hack and slash with several bosses that drop interesting (balanced) items (I'm a purist). The crypt is intended for level 20+ characters but it can be done at lower level if you're careful.

The two NPC, Zippy and Nami, are interesting though.

Zippy the ingredient sorting mouse, just click and zoom all the ingredients in your inventory are sorted into the jars.

Nami the Librarian will auto-sort all the books in your inventory. Just talk to her like you would Zippy and in the blink of an eye she makes duplicates of your books, places the copies on the shelves in a nice orderly fashion and places all the originals into one of three alphabetized closets.