w203 c230K brake questions

[sd300td]

Went to the dealership yesterday for a rough idle and check engine light issue. Turns out that there is an "open campaign" to replace some high-pressure air intake hose(s). I LOVE how they call an ordinary recall, an "open campaign". Spin spin spin.

Anywho, the SA calls and tells me that the brake pads are at 4mm front and rear, and the front discs are below spec (when asked he could not give me the measurement). I have noticed some grooving on the front discs, so am not completely surprised that the brakes might need attention.

I researched and found a post online (mbshop?) regarding specs, but wonder if anyone here can offer advice.

1. SA says that 4mm is worth about 2,500 miles front, 4,500 rear. OK?
2. What is the limit for brake pads?
3. Why hasn't the brake-wear indicator lit up yet?
4. Does anybody know the front and rear wear limits for discs? An mbshop post said 25.4 front and 8.3 rear; but I think you guys are smarter so any confirmation would be great.
5. What's a reasonable (indy shop) price to pay for front rotors, and 4 pads? This particular w203 has the cross drilled front discs.

I've been led to believe that these brakes are relatively easy to DIY, so am considering all options, etc. The one option I'm not considering is paying $975 for the dealer to do the service.

Thanks in advance.