I should back up a little. There's two ways to remove the shims: with a valve adjustment tool set or by removing the camshafts. The valve adjustment tools look like a pair of curved pliers with a small pick, you compress the valve bucket (but not pinning down the shim) and then you use the small pick and wedge it on the small knife edge of the bucket against the bottom of the camshaft shaft. If you do it right, the pliers will release and hold the bucket down but not the shim, allowing you to pop it out with a small screwdriver and magnet. Takes a good 20 tries before you get it right the first time though, very frustrating.

If you want to remove the camshafts, the whole engine has to be torn apart. Fan, belts, timing cover, timing belt, tensioner, it's a long list of parts in addition to the top end parts that need to removed to access both valve covers. Basically stripping it down to a long block at that point. However, you just measure the gaps, unbolt the camshafts and the shim are just sitting there to swap in and out.

Either way, both are big jobs that would take a lot of time. I would not recommend having a shop do due to the labor costs alone.