[nemoforone]

As most of you know, I'm a recent convert. I'm pretty decided to practice Sunni Islam.

Good choice masha'Allah, as Sunni Islam is Islam itself, the same Islam revealed by Allah to His Beloved Prophet Muhammad

I've heard that it's okay to attend a Shia Masjid, is this true? Is there anything special we're supposed to do when attending there? Any general commentary would be lovely on this. JazakAllah Khair!

I would strongly discourage you from attending their temple: Shi'ahs hold severily deviant beliefs, on the basis of which many great scholars of Islam considered them out of the folds of Islam.
It would be very dangerous to expose yourself (especially as you masha'Allah are a recent convert) to the risk of being influenced by their deviant beliefs.