Killing WK guards at towers and EPIC part : Jeb's Seal

[rustyfingers]

Hey guys, I am planning to kill the West Karana guards at towers for XP ( the ones on queynos faction ) Apparently the first part of epic ,Jeb's Seal, is optional. Anyone can confirm that since one NPC Chrislin Baker is involved in the optional part and she happens to be on same faction than the queynos guards I'm planning to kill.
I dont want to ruin my queynos faction if I need that first optional part.