I'm looking to replace the bushings on the rocker of my Trek Top Fuel 9 2008.

Has anyone done this or had experience of the same for similar treks?

Is it worth replacing all of the bushings, axle bolts and main pivot bearing at the same time, or can I get away with just doing the rocker bushings?

My trek dealer haven't been too helpful so far.

Roughly how much does it cost to have the whole lot done at a trek dealer?

Just did the rocker bearings on an older Trek, normally they'll try to sell you complete rocker arms(expensive and unavailable for that model). The bearings cost about £4 each, and about £20 labour.
Depends on the state of the rest as to whether they're worth changing, can't give a price off the top of my head, but know it's a bit pricey.

I just did the ones around the rocker on my 07 topfuel 8. They cost hardly anything from my LBS. They are just plastic top hat ones that you can press in by hand, no special tools needed.
I changed them as the rear end had movement that you could actually feel most when it was locked out at the shock, plus the bolts on the rocker would not stay tight.
It was a five minute job to install them, but took longer to clean the rocker and bolts properly, plus I put locktite on the bolts to keep everything in place. If you are not sure if the main pivot bearing needs replacing I would take off the rocker and move the back end of the bike by hand to see if it feels notchy, mine was fine.