A second second profession?

I've got a char that I'm doin more stuff with in the dessert. I just did something called A mesmers Path. The Npc then goes on about another proffesion. My question is, does this mean I get another second proffession or does it replace the one I already have? I really dont feel like messing up the one I already have, but it does peak my interest.

It'll replace your current second profession. If you already completed this mission and changed to a mesmer, you can also change back to your original secondary and get all the skills you lost back. So theoretically, you could unlock every single skill with just one character by switching secondaries (you can do it indefinitely). In practice, it's not that easy since you'd have to gain all those skill points.

You can only have one second profession at a time and access to one secondary class's skills.

It replaces the second profession you have right now and gives you the basic set of skills that would come with playing that perticular profession in pre-searing.