Well, I replaced one of the front hubs on my 52 plate Vectra C yesterday and all in all it went quite well, so I thought I'd share my experience...
Having searched the posts on this forum the main problems people were having seemed to be removing the hub nut and getting the hub off the drive shaft splines.
...the hub nut came off with no problem, I just use a 2ft breaker bar (and 32mm deep socket...) and it didn't even take my full body weight to move it!
Getting the hub off the drive shaft took a bit more effort. It was well and truly on, so i put a piece of wood across the hub resting on the end of the shaft, then put two G clamps on the wood, with the other end of the clamps on the back of the steering knuckle. Once I'd tightened up the clamps to the point of starting to bend the wood (I was using a 1 inch thick scarp of hardwood) I just gently tapped the wood at the point over the drive shaft end and off it came.
After that I counldn't get the hub out of the steering knuckle, so I took the whole knucke, off the car, turned it upside down resting on some pieces of wood and knocked it out from the back. It was pretty corroded into the knuckle, so I ended up spending a good half hour cleaning the knuckle pefore putting the new one in.
While I was at it (
) I also replaced both wishbones, droplinks and track rod ends, so all in all turned into a long day...
Hope this helps anyone thinking about changing a hub.