once u changed job, your skill tree will auto reset so u won't need to buy skill reset anymore.

old character for free mount? CC won't be so kind so NO mount for old char.

mostly public party won't get a crus/guardian for nest/raid.. my 2 fix team cleared ddn normal and hc without tanker(crus/guardian).. but if BDN, people will get Guardian>Crusader.

if you really want to start a new job and easily to get into party(public party) i had few suggestion to you,

Light Fury(supporting+heal) , Majesty(dps+BT), Raven ( pure dps), Kali(dance 2 + dps) or Artillery.

this few job were easily go get into public teams.. so good luck.