Your old r-22 unit is obsolete, if you need a new condensor or coil your probably out of luck. r-22 is no longer being manufactured but still available. unfortunately if you need to replace your unit they are being replaced with r-410a , what does this mean? it means you will have to change the whole system to a new 410a unit for it to be compatible and efficient. converting is not a good option.most components are not compatible with 410a and will not be efficient so replacement of the whole system is the only way to go.
i have been asked about converting and it is very expensive and really just a bad idea. why do that when you could have a brand new efficient system instead of your old inefficient system. besides the newer units are alot more efficient than they were even 5 years ago.