If you complete the story mode in Oblivion can you keep on playing then

Yes,you can... find side missions the people in them will give u rewards if u fulfull them. Some are optional, example:
Elf dude: Hey,you
yes you! I need help and you look perfect for the job.Help me out?


Character:I don't want to get involved/ Sure, I'll do it!


If you click no, the mission statment will come up saying, QUEST COMPLETED... You Sid u didnt want to get involved!!!
Its So Stupid!!!