need advice just got a used mazda 6

hi guys i just bought a used 2004 mazda 6 s hatch with 101,000 miles 5spd auto manual with overdrive, leather seats, heats seats, sun roof, bose system, the brakes and rotors seem to be bad, should i purchse new stock mazda brakes and pads or from somehere else, and i was wondering if i should change to time belt to timing chain and if so how much would these stuff cost. it seems like the car it using a timing belt, ould it be better or worse if i change it to timing chain?
and one more thing anyone got a picture or details about the stock car battery, cuz i think they changed it, i anna know if they put in a good battery. the battery was covered up a lil by stuff all i see in front is a green racing car picture and 85
what else do i need to check on a used car

Brakes - if you want good brakes invest in some slotted/drilled rotors with good pads. There are many companies that make a good rotor pad combo and its priced decenlty, sometimes better than the stockers. If you just want it to work then the good ol' Autozone ones will be fine.
Timing Belt/Chain - I don't think you can go from belt to chain or vise versa. you'd have to change out all those pulleys and find a chain/belt that would fit properly. As far as changing it goes, if it is belt driven then you can visually inspect it to see if there is any amount of wear and tear. If it is chain driven then you should be fine, should have it inspected though.
and BTW the 6 is chain driven.

Your car uses a Timing Chain...the last belt driven 6 was the 626