I played Oblivion first, then Morrowind. It took a bit of getting used to how important fatigue is in Morrowind and the unlevelled content was a surprise, since every enemy in Oblivion starts out pretty weak. I died a lot more at first in Morrowind than ever in Oblivion, but once I got used to the Morrowind system, which took about a week, I died a lot less. I now run a heavily modded game and enjoy it very much. Remember to keep your green bar full and fight with weapons you have some skill in (at least about 35 points) and you should do fine.
In order to use the healing ring (or any cast on use enchanted object), you need to first equip it in the magic menu. You equip such items the same way as a spell by finding the item you want equipped in the list and clicking on it. This is an additional step to equipping the item in the inventory. Once you have equipped your spell or cast on use enchanted item, you hit R to ready magic (your character will raise his hands) then you need to left click to actually cast the spell or cast on use enchantment.
The Morrowind Code Patch has a tweak you can set to cast spells or cast on use enchantments by simply hitting the R button and bypassing the extra step of left clicking.