I'm running release 12.4.23, specifically c2800nm-adventerprisek9_ivs-mz.124-23.binSome of the commands may be different since the guide is for 12.2, however, the 'Starting a Gatekeeper' and example commands appear to be the same.
I'm in the same boat as you, here is a link to some gatekeeper info.http://www.cisco.com/en/US/docs/ios/12_2/voice/configuration/guide/vvf323gk.htmlHopefully the 'Starting a Gatekeeper' and 'Configuring a Gatekeeper Example' sections will be helpful.