a page where my posts display inline 3 in a row Options

[altar]

Hi all,
I'm trying to make a specific page on my Wordpress blog where the posts, instead of displaying one on top of the other, would didsplay inline 3 in a row. It is to post images, all of the same size , so the effect would be like a gallery of some sort.
I'm also trying to get some help on the wordpress forums of course, but it's hard to get info so I thought I'd try here too, hope nobody minds...
Until now, I think that I understand that I will need a new page template php file and some css styling. I'm confused about the how I'm going to clear the divs every 3 posts to then drop and start a new line. I thought that I should clear it in the page template php file, but I've been advised to create a clearer class in the css file that I could call at the end of every third post. Which method would be best?
Also, if I create new css information for that specific page, must I create another style.css file (ex. style2.css) or is there a way to include that "page-specific" information in the existing style.css file without messing up the usual layout?
Thanks a lot