Barbarossa, don't confuse being a newbie with being a noob. Noobs are the people that get online who think everything should be easy and expect that experienced people must be hiding the secrets from them. The noobs are the ones that think it's ok to run around like other people owe them something.
You don't come across as a noob in this thread at all. Just a newbie with a few questions.
As far as YouTube banning your IP for making a bunch of spam comments, it isn't real likely at first. The most likely thing that'll happen is to get your account shutdown or possibly just limited so you can't make more comments for awhile.
If when that happens you immediately make a new account and just start making the spammy comments again, or if you make a bunch of accounts on the same IP and use them all to make those spammy comments then yeah you might get your IP address blocked.
Using proxies is a good idea if your planning to do a lot of comment spamming. You'll actually need to watch out for more than jsut changing the IP though. You'll need to delete any cookies and other tracking info being left on your pc between each IP change as well.
Just go read through the threads in the YouTube, Craigslist, and Proxies subforums. Those forums are where you'll find the most info about what to watch for when changing proxies.
Good Luck to you.