I think it depends on what you want to do. I believe Noah has said that all previous members are welcome back, even if they left the community. If you want to go back to your previous house (which was Ravenclaw, wasn't it?) then I suppose you can just rejoin, but you can be resorted if you'd like :) Either way, you'll have to go register your wand at ministry_elite so the head honchos will know you're coming back.