I bought a new dedicated server from theplanet a few weeks ago... (centos, with no installed cpanel/whm)
I set up my site to /var/www/html, and it's fully functional when accessed directly over ip...

now I need help with setting up my domain to point to the host, but using my own nameservers...
I find online tutorials too complicated, and I tried setting it all up with webmin, but with no luck...

so what is the easiest way to do that, and where should I start?

If you have only 1 domain pointing there you can just add the A records pointing to that IP. Your nameservers would point to the IP of your server.

Definately not the ideal setup but it would work. I would reccomend you just grab cpanel or another control panel if you dont know that much about config's for a plain server, it will save you much time and headache.