how hard is it to replace the small end bearings on set of standard conrods, i have a press, is it something i can do myself or do i need some special piece of kit?
You may need to find an engineer mate.
When you buy them they come oversized. Once they are pressed in they will each need machining out to match the gudgeon pins.
I paid about a tenner a rod to have mine fitted and machined at an engineering shop.