Best changes on Campag gears for easier climbing?
 

I've had a custom-built F.W. Evans touring bike for about 12 years. It's still a tremendous bike and the Campagnolo gearing is fine for touring on the flat, but not great for climbing. It was difficult enough getting over the New Zealand alps a decade ago, and I'm not getting any younger ... so would like some advice on what changes would be best.

Current gear set-up (details just read from the gears):

Campagnolo Mirage 170 CHAINWHEEL
3 ring
OUTER - 52/42
MIDDLE - 42/32
INNER - 32 - C9

Campagnolo 8-speed REAR SPROCKET
26-A, 23-A, 21-A, 19, 17, 16, 15, 14-A

Would I be better off changing the chainwheel or the sprocket?
What configuration would improve the gearing for hill climbing?
I assume it's cheaper to change the rear sprocket? Is this correct? (I want to get the best bang-for-bucks)

Thanks