About Refrigerant in Rover 75

Hello, I am the owner of a rover 75 of 2001 and I would like to know how to change the refrigerant, I have seen that the radiator wears a sleeve down to the left, but to access there you have to disassemble the Carter cover. There is no more comfortable way and after changing it, you have to purge the circuit? Is there any button for it?
Thank you

You have to disassemble the Carter cover is the only perhaps more comfortable to drain the refrigerant, the same happens, you can drain it through the lower hoses, but you must also remove the cover cover ..
greetings