Treants in SK faction hits
 

As an enchanter, should i be worried killing treants ? Do they lower the corrupt qeynos guards or the good ones? How bad would it be if i kill them for like 3 levels - and do they still give good money?

They give great money and I wouldn't worry,guards of qeynos is easy to fix when your done ruining it.
Just make sure you invis before you get druid ports into nk,surefall.

Guards of Qeynos (-1) - extremely easy to raise
Jaggedpine Treefolk (-2) - kill gnolls
Protectors of Pine (-1) - difficult to raise
QRG Protected Animals (-1) - pointless faction

not sure if you need both or only 1 of the surefall factions to be ported without invis, I would bet on jaggedpine treefolk though