What else would it be advisable to replace when replacing the two? I've already bought valve cover gaskets, and have been told to replace the oil seals. Anything else to add to the list? Thanks.

 

you cant replace valve guides without cylinder head removal. So you'll need an entire upper engine gasket kit. Also, it would be helpful if you told us what you're driving.

 

Sure, it's a 2000 Pajero/Montero with a 12-valve 6G72.

 

You will also probably need to recut the seats and grind the valves if they are not new to make sure there is a good seal between the two. When you replace the guides the center point can change enough to cause problems.