on the unique weapons sets it says one per charcter does that mean if i sell it i cant have it again unless i make a new charcter or can i sell it then aquire it again???

It means that you may only have item of that type in your character's inventory.

If it is a reward you would have to decide it's valuable, but bound items can't be sold. Mission rewards can be trashed and so ec earned. You would then just need to run the mission again for them. I've done that stacks of times. Missions with Deflectors and Shields pay nicely.

The best thing to do is always gauge the value of something in zone chat or on the exchange before making any rash decisions.

Hope that helps.

i think i know what you mean like the jeh'hadar set i could sell then re-do the mission to get it back???

Yea the Jem'Hadar and Breen sets you can redo the mission to get back. There is only a few mission rewards that you can't get again, but those are normally gotten during the 1st run or an official rerun of the featured episodes (the only other one is the Dominion Doff Pack from 4028, you can't get that twice no matter when you did the mission.)