some other mercenary questions

1:
how do i replace them, i have character 2 as a mercenary hero on character 1, what do i have to do to make character 3 a mercenary hero for character 1? if i have only 1 mercenary slot

2:
do the builds transfer? so i can use pve only skills?

1) I don't have a merc slot yet, but would guess you go back to the person you registered with. Don't forget to remove runes etc.

2) No PvE skills on heroes.

if you only have 1 slot and you want to change the merc, then go back to the mercenary registrar and change it

the merc is account wide, so if you make a merc of characer #1, then charcters 2-whatever can choose that merc. if you delete that merc to create a merc of character 2, then characters 1 and 3-whatever can use the merc.

mercs are just heroes with the skin of one of your toons, and heroes can't use PvE skills, so no

and i won't have to delete my characters if i delete it as merch?

no of course not.

do mercs gain exp/rep as well?

ie, if i play on a warrior with an ele mercenary (also me) & complete shards of orr, do both characters get the associated reputation for defeating the dungeon? same for vanquishes with bounties up?

if not, that's disappointing.

and if my normal character of lvl 20 wears starter armor, will he have max armor if i use him as merch? just like other heroes?

When you convert your level 20 character to a merc, it will have all 5 armor slots filled with max armor for its class just like every other hero does. It doesn't matter what armor you had on when you created the merc template. You can even be "naked" (in which case your merc will look "naked" but still be functionally unimpacted). What you wear when making the merc is purely for cosmetic effect.

only your active character gains the benefits of having completed vanquishes/dungeons, as mercenaries are essentially just hero templates using another character's skins, the achievements do not carry over to the 'stencil' characters.