Do I need to replace the garage door opener or just the remotes to upgrade to rolling code technology?
I'm not sure it makes sense to spend money and effort retrofitting something on a 30 year old opener. How much longer do you think it will really last? New garage door openers can be had for around $150 and in addition to the "rolling code" remotes will include several other benefits like an electric eye safety sensor, auto-reversing contact sensor, vacation lockout controls, etc. If you want to spend more you can get other bells and whistles like quiet belt drives, wifi control, number keypads, battery backup...