There are no such things as "stupid" questions. However if you think your question is a bit stupid, then this is the right place for you to post it. Please stick to easy to-the-point questions that you feel people can answer fast. For long and complicated questions prefer the other forums within the support section. Before you post please read how to get help
generally level 3 updates are safe, it's the level 4 and 5 updates that you have to be careful of. If it shows up in the MintUpdate tool, you are most likely safe, but always look over updates before you install them.
The only real issues you may have are kernel updates, they can sometimes cause the video drivers to go haywire.