In Boston or Washington DC, I expect that r134 will work out pretty good. If you are in Texas or Florida, etc, you will lose enough capacity that you will be uncomfortable most of the time unless you drive only long trips. You can regain the lost capacity from the conversion by adding about 20% more condensor capacity. I'm not sure if a condensor that large will fit in the location available.

If you are converting, it's nice to change to barrier hoses, but not usually totally necessary. The main thing is to flush the system, use compatible o-rings, an r134 drier and drain the oil out of the compresser. You then put in r134 compatible oil. If you have COMPLETELY flushed the system in the conversion, you can use PAG oil. If you're taking the shortcut and not flushing and replacing the drier, you will be forced to use ester oil to be compatible with the left over mineral oil. Oh yes, go to www.acsource.com and get the brass adapter fittings to go from 1/4" inverted flare to the bayonet type r134 fittings.

A great source of information is the bulletin board at www.aircondition.com, the best source for auto a/c goods that I've found www.acsource.com.

BTW, for flushing, you can get a cannister with air chuck and schrader valve that lets you pour in the flush, pressurize the cannister through the shrader valve, then spray with the spray chuck throught the opened components. When resealing everything, use the green r134 compatible o-rings. You can get a kit of o-rings and special glandular lubricant for $20 or so. It is well worth it.

Best of luck,