First off, as is quite apparent from the relevant thread, there is another Steam sale which offers Morrowind: Game Of The Year Edition for quite a cheap price. As such, I want to know whether or not it is worth a purchase? I've only played Skyrim, and a tiny bit of Oblivion which I did not enjoy because it was back before I was an actual, and I was wondering whether Morrowind still holds its own. Also, if it is worth a purchase, are there any mods that I should utilise? If it is anything like Oblivion or Skyrim, then most people recommend a few mods - even if it is just a UI change or something simple.

Yes, it is definitely worth $4.99. It's worth many times that, but there's not doubt it's worth a 5-spot. Regarding mods,http://www.gamesas.com/forum/12-morrowind-mods/. There is an entire forum dedicated to Morrowind mods. Also, http://www.gamesas.com/topic/1305729-mod-recommendations-for-new-players/ has mod recommendations for new players.

Okay. Thanks. Naturally, because I've never played any of it, I'm not looking for additional content as such. I was more referring to graphical or UI overhauls, or perhaps mods which fix awkward, bad or broken parts of gameplay. For example, there is the Unofficial Oblivion Patch.

I just edited my post... look at the mod recommendations for new players link.

Morrowind is very very different than Skyrim. So don't expect the same game.
You should read through here to see some of the gameplay changes: http://www.uesp.net/wiki/Differences_Between_Morrowind,_Oblivion,_and_Skyrim

Is it worth it? Very much so.
Check the Mod Recommendation link above for info on where to find patches/tools/mods/etc to update the game's textures and fix bugs.

Why do you need a UI mod? Especially since you've never even played the game yet
The Code Patch has a few little improvements for the UI, and you can change the colors if you like, but that's all it needs.

You won't need any! Unlike Oblivion or Skyrim, which have lots of tabs and scrolling, Morrowind UI is very PC friendly. When you bring up the menus, you can see your stats, map, spells and the inventory at the same time, in separate, moveable and resizeable windows.

It's worth it. The only things I would change are the graphics which are dated IMHO.

A basic upgrade would be the CodePatch, MGE-XE, Better Bodies and a head replacer (like Better Heads but there are other newer ones too)