Need guidance from the experts out there...

Recently I had a 9000btu mini-split heat pump installed it was contracted out to various parites. Supposedly the compressor is a good unit and is screw/scroll. Here is a url that shows some of them:

http://www.airconditioner.com/MINI_SPLITS.asp

Anyway, it was installed w/o incident and worked like a charm for a few weeks. Extremely quiet and able to cool my bedroom down to mid 60's. 2 Weeks after installation, I happen to have noticed that below one of the flair connections was a spot of oil (confirmed by the slick fitting). I could not get the original installer due to scheduling so I contacted a major appliance repair (ie, major appliance retailor) and stated that the system was not cooling as well as it did previously. When the technician came, I showed them what I had found. After some measurements, he concluded that R22 had been lost and proceeded to charge which made sense. He measured the cold side temp, the indoor ambient temp, and the temperature of the discharge air to determine how much to charge. After about 2 or so pounds of R22 (seemed like a lot for a 9000 btu system), he concluded that the system was really low (not sure but the split systems do not hold much more than a wall unit). The unit ran/cooled fine and produced a steady hum which was as before.

Everything was fine for a couple of days. I started to notice a vibrating sound coming from the compressor unit..the sound came and went around 2 times per second. I could not find any loose screws or panel. I felt the lines and the vibration seemed internal. Things progressively got worse and the compressor would not start. It would try for about 3 seconds but all I heard was what seemed like a stalled or locked system trying to start every minute or so...this condition sounds like a stalled electric motor.

I called the same retailer and got a different technician. He proceded to empty the system and tried to get the compressor to start...He emptied over 1 pound of R22 (did not indicate exactly how much which I found curious because the previous tech knew to the ounce how much he put in). The system finally started but I noticed the same vibration from before but it was not as loud or noticeable. It was not a loud vibration but it appeared that something still was not right. The tech emptied more R22 but the sound did not go away altogether. I am mechanical engineer and not an hvac expert so I voiced my concern and questioned whether the overfilling had damaged the screw/compressor unit and the tech said everything was fine. The vibration stayed steady but two days later, the unit once again will not start and seems to exhibit the same locked condition. I have a few very basic questions....

Is it likely that the compressor was damaged by overfilling it? If the units can be damaged in this manner, how does the damage occur? Interestingly enough, this retailer does not mention anything about this possibility but I think there might be bias because this effectively would put the accountability squarly in their court...

Assuming there is damage due to overfilling, should the ratailer try to get the manufacture to cover via warantee or should they cover the cost since they over filled the unit which possibly damaged it? Honestly, I do not want them taking anything apart...I think it would be best to replace the entire outdoor unit (comments?).

The unit is under a 3 year warantee but my concern is that the retailor is going to say its a bad compressor and the manafacturer is going to say it was damaged by overfilling (if indeed this can be detected). There were several parties involved in the installation (mistake number 1 which is a big lesson for me) but logic tells me that this unit was damaged by overcharging since it NEVER NEVER made any vibration noises prior to charging it after the leak was found...

I have the first guy from the retailer coming out again (the guy that overcharged the system). Any thoughts or suggestions are welcome! At this point, I am trying to focus on whether unit is deffective or whether it was likely damaged by the major appliance retailor. I personally think that overfilling it damaged the compressor and the compressor is on its last legs (who knows if it will ever start at this point) but I am no expert. I cannot afford any down time as this is my bedroom unit and its hot enough to where I have to have a good air conditioner to sleep.

I have definately learned my lesson and will have a 1 stop shop that does the purchase, installation, testing, service, etc for future units but need your help and expertise on this one. Thanks!