This is how I would do it.
If you want to keep your existing saves;
1. De-activate all your mods. This includes any OMODS via OBMM, or de-activating mods in BASH.
2. Make clean saves of all your characters. Copy the Documents/My Games/Oblivion/Saves folder to a safe location.
3. Uninstall any utilities tied to Oblivion, ie; OBMM, Wrye Bash (and python), BOSS, the CS, etc.
4. Run the Uninstaller from the disk (if you have it) or from Control Panel - Uninstall Programs.
5. Clean up the remaining files by deleting the Oblivion game folder, the AppData/Local/Oblivion folder and the Documents/My Games/Oblivion folder.
6. You now have a clean slate to re-install from scratch.
7. Copy your Saves folder back afterward.
If you don't want to keep your existing saves; Follow the same steps, excluding 2 + 7.