That manual isn't for your boiler @james19000 , look at the picture and then you boiler
As you have marked -
DHW outlet is actually the cold water inlet
Return is actually the DHW outlet
Gas is OK
The 2 outside 22mm pipe's (marked flow and DHW inlet) are the 2 to isolate. If you aren't changing the radiator valves though then you don't need to isolate the boiler, just isolate the rad valves, drain it down and replace.