Alternator
 

So today was a pretty lame day. My alternator went out while I was out taking care of some errands. So I am forced to replace it so I can make it to my job (45 miles away). This mechanic that I have went to a few times for some minor work i.e. (vacuum lines, minor oil leak) quoted me 500-550 including labor to do the job. Now I like this guy but I want to make sure I am not being taken advantage of because I am quite naive when it comes to cars. Definitely not a mechanic haha. What do you all think? I am going to be doing this within 2 days so any feed back would be greatly appreciated!! Thanks.

2003 A6 2.7T that would probably help!