Want to buy M3 E46

Hi Guys!

i am new to this forum and I want to buy a M3E46 SMG...would also take a CSL...

I have some questions:

What is the actual price range for normal M3 and CSL?
Can you advise a good workshop to do maintenance works?
Where do I get engine tune up (carbon air box, Camshafts, installation, set up on dyno)?
Where do I get a nice exhaust? Original sound is horrible I think...

Would be great to receive some advises, many thanks!