pressure

Its a 2007 honda element only $28,000 on it. I know not a lot of miles. I work from home 90% of the time. So, what is the pressure level the ac is to be at. I got one of those fill your own ac kits. ArcticFreeze Ultra Synthetic Refrigerant 134a+ (what the hell is the plus for?) Its at 30 which...

I had the flashin "D" light so I had it diagnosed by the dealer (autozone cant do trans diag apparently as it came up "no codes")and they said it's the 3rd gear pressure switch. They wanted $318 to replace it and do a fluid change so I'm doing it myself as the diff fluid is due too. Which of...