As long as you flush the system of the old debris, add 8oz of new PAG or Ester oil, replace the accumulator, you shouldn't have any problem with the compressor with r134a. Of course the only way to know if the compressor is weak and not on the way out is either to dissassemble and inspect it in a dust free room, or charge it up and take pressure readings, or just chance it.
Just converting over won't necessarily cause the compressor to go. r134A does run at a higher pressure, so if the compressor is old and already has signs of sress, retrofitting certainly won't help it live longer
Generally, what prompts people to swap over is blown compressor (lack of oil is what causes this 90% of the time) and the higher cost of refilling with r12.
And most certainly your system
can be retrofitted with r134A. It costs a bit up front to do a proper conversion, or... you can spend $35 for a kit to get a years worth of cooling and then swap out the whole A/C system firewall forward when the compressor blows. What I would advise is this: get a quote to leak test and recharge with r12. And then get a quote to retrofit with r134a and compare.
Here's what you should look for on all quotes:
Orings
leak test (this can be determined by pulling a vaccum later)
add mineral oil (R12) or PAG/POE (R134a)
- some amount of compatible oil should ALWAYS be added
new accumulator (they're not pulling your chain; there's a good reason for it)
cost to recharge (vaccuum the system and charge with refrigerant)
cost of refrigerant
To retrofit, there are some additional costs:
system flush,
compatible fittings.
All of this assumues that nothing is broken and that any leaks are confined to the Oring joints. If any leak is found in the compressor, the condenser, or the evaporator, it will cost more.
You might find that continuing with r12 isn't necessarily more expensive. This much is for sure, r12 will tend to work better on your car.
And FYI, your car takes 40oz (2.5lbs) of r12.
If you use r134a, expect to use 32-35oz.
Hope this helps.