I have a few questions on my Roth IRA quest.

I started funding it this year and I'm 2/3rd of the way done and pretty excited. What worries me more is what I don't understand about the way the Roth functions in retirement years when one can take out their holdings.

Is my understanding correct that if I were to have 500k for example at the age of 60, I could simply take the value or do I actually have to make trades in order to take out money from my Roth? I'm not including (but thinking about withdrawal rates and a certain income that I'd be taking out yearly hopefully 30-40k). I'm too young to really know my future needs but I would appreciate clarification for those in or nearing retirement who are making use of their IRA perhaps.

Also who actually governs or controls the amount that one puts in an IRA on a yearly basis. Sure I understand that 3k can be invested for those under 50 and 3.5k with more to come for those older, but because I use Scottrade there doesn't seem to be an "authority" that caps this. Not that I want to, but if I were to put 5k in my IRA this year, who gives me a slap on the hand if anyone? Thanks.