You shouldn't need to replace the "tappets" which the 1UZ doesn't really have.
You could have to replace the followers/buckets due to wear but this would very rare.
Usually the shims need replacing, which is the equivalent of setting the valve clearance on a pushrod engine.
To get the buckets out you need to remove the camshafts.
To do that you need to release the cam belt remove the distributors then remove the cams.
Getting it all apart is quite easy but you need to start with the engine on TDC so you can it all back together.
Reassembly will require clear instructions as it is easy to get it wrong.
Make sure your mate is comfortable witht he procedure before diving in.
You are more likely to find it just needs the clearances set correctly by replacing the shims or swapping them around.
There's a tutorial around here someplace on how to do it.