it highly depends on your unit if they want to send u for guards conversion course. either you carry balls and volunteer, or kenna forced by OC, or you're a regular.
alright, after signal course (officer, spec or man), you'd be posted to active units (in this case a guards battalion or brigade). from here, if there's a upcoming intake of GCC (for officer and spec is one group), your signal OC might task you to take it up if you're a regular. as for NSFs, if you're on the ball, wanna be garang, wanna hao lian wear guards tab, by all means volunteer. it you've gone thru sispec or ocs, GCC should be no problems.
after GCC, your vocation will still be under support signal but wear your guards tab with pride. so those combat fellow guardsmen (officer, spec or men), will not look down or make things difficult for you when you do things. coz u underwent the hardship and the rapport comraderie with other GCC coursemates (fellow officers and specs) will help you in future dealings within the guards unit.
many years ago, i too wanted to go for the GCC course when i first posted to the brigade. saw my fellow sispec mates who were snipers, lightstrike, scout all went for it. but sad lonely me in signal like kenna outcast... somemore i gold ippt run 9min one leh. haiz... kenna discouraged by fellow older signal spec and officers say many things to do in the company, no time to send me to such "bo liao" course.
anyway, during my time, the brigade NSF medical officer underwent guards and ranger course. see him wear the number 3 like damn garang.