As much as I’d like to say it’s really hard and to pay me to do it 
the fact is it’s a cinch. Go to the CLA on Yanping north road with your documents and 500NT and you’ll be set within 5~7 working days. They’ll give you a work permit which you can then take over to the NIA to extend your ARC. If you want the list of needed docs look at my update to this post from a couple months back, it should all be there.
I agree with Llary that there seems to be no need to renew the office itself, however it might be prudent to double check with the MOEA. A quick email should suffice!
Edit: Just to plug myself for a second:
