The shortest way is to go via Bathurst. From there you go to Oberon via Taralga. Undulating country, but nothing seriously steep. You don't go all the way into Bathurst - about 5 km short of the town centre, you turn Right and head to Sofala. This section of the road is hilly, but it has a good alignment. From Sofala, you continue on to Ilford (the road is hilly), where you turn left and it is an easy run into Mudgee. Allow about 4 hours driving time from Goulburn to Mudgee. The road is sealed all the way, but as said, is hilly in places. The hills are really not that much worse than if you were to go into Sydney and pick up the M4 to get out to Lithgow, and you have very little traffic to contend with.

An alternative route from Goulburn to Bathurst is to go via Crookwell. I believe that this road is now sealed all the way as well. There is a steep climb at Abercombie caves, but after that it is an easy run into Bathurst. Near Crookwell, there is a large wind farm and you get reasonably close to the wind turbines. They are BIG.

A lot of the run into Bathurst is at an elevation around 1200 m above sea level. This area gets snow in winter, so if it has been a bit beastly, check with the RTA roads website for any road closures. The road is normally open, but when really bad storms come through you could get some snow.

Thanks