seem that u did abit of reading, but not enough. read more!
alrite, its better, better and better to have a skimmer running to have a healthy reef tank.
sump is advisable to have as it able to provide more water volume(so that ur tank wont crush easily when something goes wrong) and u are able to hide ur equipments into it.
overhead filter? if im you, i will change the filter wool or wash it like once or twice every 2 weeks.
and if u are using bio-sponge or bioballs in ur filter, u will find nitrate and stuck dentris problems sooner or later.
good luck man and have fun setting one up.
just shoot this forum with questions if u are in doubts.
happy reefing.