Cam Pully bearing has gone out on my car. How hard to replace it?

What engine? The 2.0I presume? The right way to do it is with the tools to hold the camshafts and the crank shaft in place, and the belt gets installed with the pulleys loose on the camshafts. It's not too bad to do for an experienced person. The 3.0 uses chains and guides, no idler pulleys.

have it done by your mech as not to poss cause other issues

Cam pulley bearing??