Changing/ore getting 1 more secondary?

I am @ a dude who wants too change my/ore give an other secondary profession (intoo) mesmer.
So when i do that then i can't use my old secondary skills anymore right.
Like i use a bow and i got 12 markmanship (that will be gone then right?)
It says that i am worthy of more then 1 seconday skill but that is just a typo right???

The guys name is eulenias in destiny's gorge