If you have a '90 model anything, then you need a conversion to R134a. You can easily tell if it's been converted by looking at the service port. If it has external threads, it's still set up for R12.

When I had my '92 Civic converted the system was evacuated, then there was a different oil used for the R134a. Some people say that changing oil is not necessary now. :dunno: Two adapters were permanently installed over the OEM ports to facilitate charging with the new stuff.

If your system has been open for a while where outside air could come in, yes you'd likely need a drier. If it's been closed, even if it's not been charged then you might not need it. The r12 drier will have a sight glass on it, but when using with R134a refrigerent, you disregard reading the bubble because it does not work the same. Simply put in the specified amount of refrigerant required for R134a, but don't just use the same as R12. (I don't know how much R134a stuff you'd need for your Accord, but that shouldn't be hard to find out)

Remember that you charge the suction side, which has the larger diameter tubing. It will have the smaller service port.

FYI, R134a will run a higher head pressure, so there's a minute chance that after you get set-up you could develop a leak somewhere in the system.

One thing to help keep the pressure down is to check your condenser to make sure it's clean (no leaves, trash)