Changing a/c drier & switches 1990 300SE; need advice

[francotirador]

I have a 1990 300SE which has an a/c leak. It stopped working yesterday and I noticed the dye around the receiver drier/accumulator. The previous owner had the system charged in '07 or '08 and they put the dye in at that time. I took the car to a shop today where they told me the a/c high/low pressure switch was bad. The cost to replace the switch and recharge the system is $340 plus tax. Instead of just replacing that switch I want to replace the temp sensor/aux fan switch and the receiver drier/accumulator also. I want to do that myself then have them charge the system. I will also replace all related o-rings and seals. I'd like to know if it's OK for me to do this job myself. I just hate having anyone replace anything anymore unless it's absolutely necessary. I've had too much bad luck with these guys not doing the job they were paid to do.