Replacing 42/52 crankset to 39/52 - will it make a difference? I have several questions that arise from the fact that the current drivetrain on my old Peugeot road bike is pretty tough to ride when climbing up some steep hills: so I've got a 42/52 up front and 6 speeds (largest: 24) on the back.

So my first question: will changing the front to e.g. 39/52 setup make a noticable difference. 

If so, can it be exchanged to e.g. some older/used crakset such as this Campa
http://apro.bikemag.hu/files/4/2/listing_photo159024_555485241366650384.jpg

It has the same tapered square connection as the current one.
You asked: will changing the front to e.g. 39/52 setup make a noticable difference?
My answer is an unequivocal 'yes'. If you can however, consider 34 or 36-tooth inner and 50T outer, if you can find chainrings that fit your spider. TA make a large range of chainrings, however new ones will probably cost more than the monetary value of your bike.