Ubuntu :: Verifying An User's Permissions?

I just started dual booting Ubuntu 10.10 on my mini 10v with OS X a couple days ago, so I'm still pretty new to Linux.

But anyhow, I was attempting to change my User ID number so I could access the files in my User folder on my OS X partition. So, I tried entering the following commands:

sudo usermod -u 501 yourusername
sudo chown -R 501 /home/yourusername

Of course, smart me should've realized I should've been logged out and on a different administrative account to do this. But I didn't, and I believe the second command didn't work. So, whatever, I thought I'd try logging out and logging in as root.

So, I logged out, tried logging in as root, and of course, no dice because I didn't know the password. So then I tried logging onto my account and upon logging in, I got two errors. One was about ".ICEauthority" and I didn't keep track of what the other one was.

Great. So I did a quick google for the error, then tried entering these codes:

$ sudo chown user:user home/user/.ICEauthority
$ sudo chmod 664 /home/user/.ICEautority
$ exit

[Code].....

And again, I think the last one didn't work. So, I looked up how to login as root, changed the password and logged in as root successfully. Then, whilst in root, I entered:

/usr/sbin/usermod -u 12345 joeuser
/usr/bin/find / -user 701 -print | xargs -t chown joeuser
/usr/bin/find / -user 701 -exec chown joeuser {} ;

Upon entering those, I logged out and logged back into my account and everything was a complete success. No error messages anywheres AND I could access the files in my Mac user folder.

So, here's my question. How can I make sure I have all the right permissions I need? Or do I already have the all of the permissions I had before changing my user id?

Did those last three lines of code I entered "override" all of the codes I had entered previously? I just want to make sure verify I have all the correct permissions necessary so I don't run into any issues later on.