I'm not sure if the uploader is fixed. But if you go to advanced reply (next to post quick reply) there will be an icon that looks like a paper clip. Click that and upload your replays. Close out of it and click the icon again and press "insert all attatchments".
As for the clan, start if with Bleu if you are looking for an official clan. No other clans will accept you.... But give it a shot if you're feelin lucky on any clan board. Many unofficial clans need members, try one of those.