Great Thread

I am a bit stuck, I am using the Free Heatmap Theme, I want to add different style of Font for my main body amd Headings I also want to change the size of my main body text and put a slighty bigger gap between text on the main body.I have opened up the Style.css.
/* Typography Set Up
-------------------------------------------------------------- */
/*
Default font settings.
The font-size percentage is of 16px. (0.75 * 16px = 12px)
-------------------------------------------------------------- */
body {
font-size: 75%;
line-height: 1.5;
width: 100%;
}
/* Headings
-------------------------------------------------------------- */
h1,h2,h3,h4,h5,h6 { font-weight: bold; color: #000; }
h1 { font-size: 1.8em; line-height: 1; margin-bottom: 0.6em;}
h2 { font-size: 1.5em; line-height: 1; margin-bottom: 0.6em; }
h3 { font-size: 1.2em; line-height: 1; margin-bottom: 0.6em; }
h4 { font-size: 1em; line-height: 1.25; margin-bottom:0.6em; }
h5 { font-size: 1em; line-height: 1.25; margin-bottom:0.6em; }
h6 { font-size: 1em; line-height: 1.25; margin-bottom:0.6em; }
h1 img, h2 img, h3 img, h4 img, h5 img, h6 img {
margin: 0;
}
I have tried to enlarge the font size in bolded text, but it just enlarges everything, I can take the formula that is used "
The font-size percentage is of 16px. (0.75 * 16px = 12px)" and adjust some of the side bars etc to make them a bit smaller after they have been enlarged, but it is far to messy. is there a way to just enlarge the main body text without it enlarging everything?
Thanks