Firstly, the redline is determined by the highest engine speed deemed safe for the motor. If it is exceeded (though we have rev limiters), the engine cannot handle the high rate of speed... it was only designed to be revved so high before parts starting breaking/blowing/etc. I am no expert though, but this is a pretty good idea.
If your car is in good mechanical order, and you have good fresh oil and GOOD TRANS FLUID (IMPORTANT) then I wouldn't worry much. I have driven the SH** out of my engine for the past 60k miles and it still drives like a dream with good maintenance. Just make sure you have good fluids... and there is a line to draw... I wouldn't do it TOO much... but your engine is a damn good motor that was designed by Mercedes engineers... the cars in Germany are driven like that ALL the time.
If you floor the gas, but no kickdown, it will change into 2nd gear below redline, about 5500 RPM. If you keep it in kickdown, floored, it will shift into 2nd at redline. If you have the shifter in 2, and floor it (no kickdown) it will shift about 100/200 RPMS shy of redline. (If in 2 and kickdown engaged, then it'll shift at redline)
Hope this helps!
2006 E350 w/ 155k miles (Daily Driver)
1993 300E 3.2L Sedan w/ close to about 300k miles
2003 E500 Brilliant Silver (Had 217k miles when totalled!)
1989 300E with 289,000 miles (had for <1 yr while in HI)
03 CLK 500 cabrio (Mom's)
2006 C230k (Dad's)
1999 S420 (Mom's/Dad's)
2000 C230k Sport sedans
2001 CLK320 Cabrio (Mom's)
1995 C280 My First Mercedes-Benz... (155k miles. EXCEPTIONAL AUTOMOBILE. Was Very hard to let go of!)