Hey jayjay
The gaskets are dealer only in the uk but you could order from rockauto in the US or any other US supplier that'll ship, but they are ony £35 ish each from dealer. You may also want new manifold gaskets if you remove the manifolds. Additional to the head gaskets, whilst you have everything off it may be prudent to do the 00m12 kit shown below which has the upper and lower intake gasket rings and an updated tensioner for the passenger side head.
The devil will be in the removal of the top bolt for the rear timing cassette guide as it is at the rear of the drivers side head.
The next issue you will have is the timing. There is a special tool kit (otc-6488) you should use to lock the cams and the crank for the removal and for the retiming post work. It also has a special tool to be able to undo the D/S cam sprocket bolt (reverse thread) as again being at the rear of the engine access is minimal.
Do some research on this site about timing the engine as this is critical and if you get it wrong you will bust a load of valves! There are a couple of guys that have done the chains without the tool kit so it's possible.
The head bolts are supposed to be single use only but after talkin to some people that said you can get away with one retorque i chanced it and have had no problem.
All in all it's not something i would like to do with the engine in the car. If you are v. handy with the spanners it's do-able, if you are not that experienced ship it to Justin at explorerpartsuk or DuncanofEngland (Duncan is a member on this forum)
Do you have any chain rattle? If you do then this may be the time to address this also and pull the engine and do it all at once.
Regards