Advice on changing break pads 2009

What the hell happened to these forums? So sad to see spam.

Anyway, hello!

On my oil change, I was informed front breaks have 9mm and rear breaks are on drums.

Should I even consider replacing both at once? And, how much do parts cost for just rears in Canada? What should I expect to pay my mechanic?

Thank you!

P.s. should I change oil every 5k kilometers or 8k with 5w20 oil?