Hello, I made some mistakes in choosing attributes/skills for myself in the tutorial, and really really really would not like to restart. Is there any way I can tweak my character's settings after the tutorial? Is there a console command like "showracemenu" in Skyrim? Or a mod I can install? Or some tweak to some file?

No at this point you are pretty much SOL, unless you want to make purely cosmetic changes.

showclassmenu, will allow you to pick a different class. It might reset you to level 1 though. I don't currently have a save file to test it on.

edit:

showclassmenu

Change Class

WARNING: Using this menu will reset all of your skills to their default initial settings. If you want to save your current skills, you'll have to open the escape menu right before clicking the final "done" button, save the game through the console (save test) and then reload it (load test). After the reload your Classes will be changed like you wanted them to be and your skills will not be reset)

Source: http://www.uesp.net/wiki/Oblivion:Console

Always a good idea to make successive saves in this game, rather than overwriting one save. Then you can always revert back to a prior state if something has gone wrong.

Also, it's a great idea to make a save at the end of the tutorial dungeon, before leaving the sewer. You get a final chance to make changes to the character at that point. And if you have a save made at that point, you can start new characters there, and not have to go through the whole tutorial.