I have a 2003 Honda accord lx. I have to replace my AC compressor bc the clutch is bad. ?

Actually, it is not mandatory for you to mess with anything in the refrigerant loop if you can get the clutch as a separate assembly. I have done that for a few cars but it has always been a lot of phone calls to find a store that can even get me the clutch separate from the compressor. The frustratingly expensive alternative is to buy a compressor with a clutch and just do a clutch swap - the source sells them for $215 to $325, depending on quality. If the refrigerant loop has to be opened it is a job for a professional. Theoretically we can work with a professional who will de-gas and recharge the system, but really the amount of labor he has to do is about the same whether he replaces the compressor himself or not. Anyway, normally the receiver/dryer is replaced whenever a compressor is replaced, but other things are not disturbed. It is best not to arouse the evil spirits any more than necessary.

It can be a cause for the compressor to not engage, if there's no pressure. The compressor will shut down if the pressure is too high as well. Its just designed to shut down when there is a change in pressure most likely yes its low on feon but if its low check the system pressure. You don't need to change the air drier and expansion valve. You can refer this link to know more Honda Accord's A/C Compressor parts: http://www.buyautoparts.com/autoparts/Honda/A-C_Compressor.html