2005 Toyota Highlander with a leaky Front Differential...what should I do?

[Durt]

I have a 2005 Toyota Highlander. I just got it back from the dealer; I brought it in to have a routine oil change and tire rotation. While it was there they discovered that I had only 1mm left on my brake pads, and I am well aware they overcharged me for the installation of new ones: my total for the oil change, tire rotation, and brake installation was $307...ridiculous. Next they told me that my Front Differential was leaking and would need to be repaired soon, as it would only get worse. I asked for a quote, and received an estimate of $1057. Considering they overcharged me for the brake job, and I do not have $1000 extra just lying around, I was wondering if anyone could give me a little insight as to whether or not they are ripping me off. I am told that to re-seal the Front Differential is time consuming, but it requires no extra parts. So, simply put, my question is this: am I getting ripped off again?