Is there a way to edit a WordPress themes font and font size that is easy? ?

I have had this theme for several years. I know how to change little things like the banner and such at the top. But, I would like to change the font size and color. Both in the body and the sidebar. Is there an easy way for a novice to do this? Here is my blog:

Thanks ahead of time!!
There seems to be a million different places to change the font in the css file. Is there a easy way to change each one or just change them all?