No bro the first guardians were the risen meaning you have to die first

Yes you can. It doesn't matter where you came from, if you have Light then you can be chosen by a Ghost. The same goes for if you're dead or alive; far more people have died than are currently alive in Destiny, so the odds of finding a dead person with Light are vastly more likely than finding a living person with Light. Shin Malphur is the only recorded Guardian to have been alive when paired with a Ghost, but it's possible that there are a couple more Guardians found like that