I want to update one of my existing sheets, not sure how.

[puggsoy]

For the first one, just post the updated sheet in the same thread and say which it needs to replace (if it isn't already obvious), and the uploaders should do it. You can also make a new icon if you want.

Secondly, yep you can post all your rips from the same game in the same thread. Some people (like me) even have a single thread where they submit all their rips from any consoles and games.