Lapsed Advanced Ground Instructor certificate, can I take a FIRC and and restore my privileges? I hold an AGI certificate that I haven't exercised the privileges for in quite some time (more than 12 calendar months).

According to 14 CFR 61.217, can I simply take a Flight Instructor Refresher Course (online or in person) and restore my privileges?


  § 61.217 Recent experience requirements. The holder of a ground
  instructor certificate may not perform the duties of a ground
  instructor unless the person can show that one of the following
  occurred during the preceding 12 calendar months:
  
  (a) Employment or activity as a ground instructor giving pilot, flight
  instructor, or ground instructor training;
  
  (b) Employment or activity as a flight instructor giving pilot, flight
  instructor, or ground instructor ground or flight training;
  
  (c) Completion of an approved flight instructor refresher course and
  receipt of a graduation certificate for that course; or
  
  (d) An endorsement from an authorized instructor certifying that the
  person has demonstrated knowledge in the subject areas prescribed
  under § 61.213(a)(3) and (a)(4), as appropriate.


It appears so, but I guess at the root of my question is, is it really that simple or did I miss a regulation or sign-off requirement somewhere (I know I could get signed off in leiu of the FIRC).

Then to keep current, what constitutes activity as a ground instructor giving pilot...training?  Just teaching and logging that I've been teaching ground school, or would I actually have had to endorse some people to take the written exam during those 12 calendar months?
First, as the regulation says, you can indeed take an FIRC to restore your privileges.

Second, I couldn't find any FAA clarification on exactly what "employment or activity as a ground instructor" means, but the language is fairly clear: you just have to be able to show that you were providing instruction as a ground instructor. That could be via training records, invoices, employment contracts, written test endorsements etc.

As a general rule, there's no need to look for extra requirements that aren't stated in the regulations.