i am a noob to the game, not the show.
just started my first character as an engeneer, but i am planning on getting a science vessel, so i
want to change my character to a science officer.
can i do that in a respec or should i create a whole new science officer character now?
i am lietenant 6 now, just played for a couple days.
thanks

No... You're stuck with the profession you choose for that Char... Respecs are for re-assigning skill only... Wich you probably don't need at this point. That said:

A Eng can fly a Sci ship, no problems... You will just not have the Sci-profession skills that would follow a sci captain.

As lt6 you may want to consider simply resolving your character. The early levels are rather quick.
As engineer in science ship you be limited by what ltmcdr and cmdr science bridge officer skills you can train. There you need some one else to train certain skills for you. If your since you can train them your self if you have enough skill points in skills that buff that power.