Is it difficult?

Mine are almost ok, but not perfect I don't think as they're very noisy, especially when cold, but just noisy all the time.

What's the process for setting them up correctly?

mine for sale in 2 weeks max and run mint

I think this is what you mean..

http://www.audi-sport.net/xf/threads/how-to-guide-pd-tdi-injector-adjustment-clearance-lash.183040/

I think this is what you mean..

http://www.audi-sport.net/xf/threads/how-to-guide-pd-tdi-injector-adjustment-clearance-lash.183040/

Exactly what I wanted. Thanks mate