Replacing brake cables isn't hard. Just need a cable cutter and a couple of cable ends to crimp on - ask your LBS, they'll have the pads too.

For simple mechanical advise and instruction:
http://www.parktool.com/repair/bikemap.asp

For info on older bikes and odd sized stuff
http://www.sheldonbrown.com

27" inch tires and tubes can be had at most Walmarts.