Go easy removing the electrical connections on the glow plugs, if they haven't been removed removed for a while they could be siezed and if they are it makes the job harder. When I first did mine the ring connector snapped off the cable on No 1 and it was a bugger to get a new one on the short length of cable.
Remove the inlet manifold to gain best access.
I buy the cheap ones, Wellmans iirc, I need to replace them every 18-24 months I would say.