Problems with Frontera

Hi all just thought I would share this...

A couple of weeks ago I had a major problem with my 4WD it was barely able to make it up the hill I live on so I took in early to the mechanic for a service his diagnosis was to get it to a Holden dealer quick smart to have it checked out as he felt it was a problem with low fuel pressure, and possibly the catalytic converter but wanted me to have it put on their computer to rule out anything else.
I did this within a couple of days and advised the team what my mechanic had already told me where upon the Holden dealer service team took off the exhaust system to check it out they found no problem.
They then decided it must be the timing belt My car has done approx. 120,000 km's and they said it probably won't be the issue as it needs replacing at 160,000 I corrected them that it is actually 140,000 km's when it needs to be replaced, they asked how I knew this and I explained that is what it say's in the manual. They said "oh well you didn't give us that" but they had not looked in the glove box for it. Any way they then told me it was not the timing belt at fault. Then they decided it must be the fuel injectors so the checked and cleaned them, but they were fine as well. Then they decided to get another Frontera and do comparative tests with it and they came across a problem with my air con... I had 12 months ago had a whole new compressor replaced and the warrantee was due to expire that day so the company that did this work trucked it from the dealer to the work shop and once fixed free of charged it was then returned to the dealer, but the problem existed.
By now it's been 10 days that have had my car and all of a sudden they decided to go back to square one and remove the exhaust again, where they discovered it was the exhaust after all and the catalytic converter that needed to be replaced as it was 90% blocked. I was quoted $1200.00 for a replacement genuine part or non for $360.00 I opted for the NGP I went to collect it the next day only to be told come back tomorrow and when doing that I was hit with a bill for $1680.00. They advised me they had to replace 2 Cat converters as the other was 50% blocked but I had not been told this at, they explained they didn't want me to have to come back after 6 months with the same problem but I replied I was only quoted for 1. They also replaced the spark plugs which had been done at the 100,000 km service as required and usually last for 100,000 km's as they are irridium.
I won't say just yet what I ended up paying for all of this but would love some feed back on weather you think that it is a fair amount? and if not what would you have been willing to pay ? and how you would have dealt with this situation.?