Depending on your isp you may well be able to change it. If youre currently given a static ip you can unplug your modem (sometimes takes 8 days) to be given a new IP.
If you have a router you could try changing the mac addy and it should work...
Its early.. hopefully on point with this one.
As for proxies, yes, you can use one if its to surf a board. Some dont allow replies and joining through them, some do. On bigger boards theyve usually been banned already since the 'trouble makers' use them