Spark plug replacement

[G8TEY]

Hi all I’m a new member I have a fresh import Toyota alphard 3.0 v6 unregistered as yet I am a mechanic but was wondering if there is a easy way of changing the rear spark plugs also going to change timing belt and water pump tomorrow I’m sure I’ve seen a guide to that somewhere what other things should I be doing I’ve fully stripped and serviced the breaks today and also under sealing tomorrow as well would like to know what under seal people recommend