RainSoft Classic Apollo...discolored and blackened water

Hi,
I have a RainSoft Classic Apollo (came with the house when I bought it).
I had it serviced recently, and since then have had rusty looking water when I first turn on the taps (hot or cold water) from any tap in the house. Over the last few days, I now have black water when I flush the toilets.
I had a plumber out today to flush the hot water heater (since I know that's the first thing RainSoft will say) and my water heater is fine.
So I called the local service company today and the girl told me (over the phone) that it sounds like I need to have the resin replaced.

First question: How often does resin need to be replaced?

Second: How can you tell resin needs to be replaced?

Third: How much should this cost?

The girl on the phone told me it will be 89.00 service call and 450.00 to replace the resin.

I feel like I'm getting ripped.

Does this sound reasonable?

Thanks.