I don't remember exactly how long ago I did it, but my primary computer runs Ubuntu and only Ubuntu. (My wfie's computer runs Vista & I have to use Win2k at work, but beyond that I'm 100% Linux)
My advice:
1) Get familiar with the command line. 99% of what you do through the GUI you can do through the command line faster and more reliably. Doesn't mean you should ditch the GUI. Buts its nice to be able to open a terminal window to run updates rather than going through Synaptic or something like that.
2) Get really good at Google Searches. 99% of the problems you will run into will have been experienced by someone else first. And the great part is that there is almost always a solution somehwere online. (Which will more than likely require you to open a terminal window and... [see #1])
3) Be patient. Its going ot take time. But you are going to get used to it. Always remember there are lots of people out there who are very willing to help you get through any issues that come up. Be nice to them and they'll be nice to you.