Check out hondaautomotiveparts.com for price, I don't know offhand...

The compressor oil is different, the stuff in a conversion kit is chosen so it's compatible with the little bit that never drains out from the compressor. The oil that they put into NEW cars is different yet, so make sure you know which one. (I don't remember which is which).

I believe there should be a sticker somewhere in the engine compartment. If it says R12 then you use about 3/4 of that amount when you go to R-134a. Sometimes if it's been converted, there's a R-134a sticker over top of that original one. (Besides the fittings being different.)