Hmm its been what.. 10 years lol? Having a hard time remembering. First off there is of course the 2 expansions. Definitely recommend those.
Best bet for mods would be to go to:
http://www.nexusmods.com/morrowind/?
It is probably the main hub for mods.
One of the first things I would do is install Better Bodies. The vanilla bodies are horrible.
Several armour replacers should be available that are based on Better bodies as well.
Texture and sound improvements are probably welcome when coming back to the game after 10 years.
If I was going back, I would most certainly look for a mod that improved the combat system. The vanilla system of having to click R(I think) to ready you hands to cast spells, and then "R" again to get weapons back out was just so clumpsy compared to newer games.
Else just try and browse the highest rated mods on the nexus and read the descriptions. I might be able to name the names of a few mods, but they might not exist anymore or have been replaced.
One thing I would have to stress is to try not and be tempted by the many "OP" mods outthere. At least not until you are well into/done with the main quests etc.
EDIT: Just remembered a few things:
http://lovkullen.net/Emma/
I remember most of those people on that site as making quality work(You might even recognise a few of the names from the MC modding scene lol). Specially Emma's and Grumpy's work still stand clear in mind now that I get it refreshed. Emma's "White wolf of Lokken" was a great quest mod back in the days.
CanadianIce did a ton of really good looking stuff, sadly mostly only for female characters(which most modders did/do, so if you like nice looking armour, considder making a female char):
http://canadianice.moddersrealm.com/
Bethesda released a row of free mods themselves to sort of get the ball rolling, definitely worth downloading:
http://www.uesp.net/wiki/Morrowind:Official_Plug-ins