Macro lens help for D90

Hi

I'm interested in getting a macro lens for my D90. One person has recommended the 60mm Nikkor D AF f2.8.

A couple of questions:

1) What's the difference between this and the G ED lens? (I don't understand much about different lenses yet as currently only have an 18-105.)

2) Is the 60mm the best one to go for, or is it the best to go for, for 'that kind of money' (ie. £260ish second hand)? In which case, would it be worth pushing to a, say, 105mm for a bit extra etc? I haven't quite got my head round the technicalities of lenses yet so please excuse my naivety! I don't know if a 105 macro would be 'better' than a 60mm.

Can anyone please help? It would be much appreciated!

thanks