I cleaned out the core last august when I had the radiator out to replace it... I worked the thing over really good with an air compressor. Blew out a lot of road salt, sand, bugs, etc... There are 2 places where about half a dozen fins max are folded...
Not sure about the oil... How would one evacuate the oil out of the system to put in the right amount?? Can that be done without taking the system apart?? Or opening it up??
I"m unsure about a compressor fail... I'm the 4th owner of the car... I don't have a receipt for one, I'll put it that way. The previous owners seemed to take good care of the car, and keep good receipts...
Would the TXV/flow piston be the same as an expansion valve??
Even r134a is hard to get here in Canada. The Canadian government is recommending that people use duracool or r12a. Something about Canada's environmental initiative...

__________________
All it takes for evil to prevail is for good men to stand by and do nothing.

Too many people tip toe through life, never attempting or doing anything great, hoping to make it safely to death... Bob Proctor

'95 S320 LWB
'87 300SDL
'04 E500 wagon 4matic