Campagnolo 10 speed Ergo levers are compatible with a Shimano 8 speed drivetrain, so you should only need to change the shifters.
Compatibility chart:
http://www.ctc.org.uk/desktopdefault.aspx?tabid=3946
Campy Ergo levers are way more affordable than Shimano STI. Best prices I've seen are on Ribble.