What I am looking to do is wire my blinker bulb to turn on whenever my side marker is on and then have the both of them blink when I use my turn signal. I looked through the how-to's and found this link.

I know a bit about electrical but don't know too much about headlight wiring. Would it be as simple as tapping the wires that go to the side marker and using those as the wires for the blinker too?

 

Instead of the one you linked to, I think this one is what you want:

http://www.vqpower.com/v2/articles.php?article_id=57

This will make your turn signal lights come on (half power) when your side marker lights come on (parking lights)...while retaining turn signal abilities. If you wanted your side marker lights to blink as well, I think you'd do BOTH of them...this one and the one you referenced.