backing up old post?

hi, i’m currently on wp 1.2.1 and i wish to upgrade it to 1.5.2. My question, i have 1 whole year of blog that i wanna keep but the installation guide doesn’t say anything about backing up the old blogs and anything about putting them back together.

is it possible to keep the old blogs and my kubrick template?? i cannot find any tutorial to do just that!