relic it sounds like you went to some studio where the guy had no idea what he was doing. Dont let your one bad experience ruin your view of all mix engineers.
No for YEARS I went to studios where they mixed rock not rap, cause rap wasnt "in" at that time, and none of those lenard skinard mixin mf'rs knew shit about hiphop, and there IS a diff, so we left frequently with it sounding good on monitors and bad on the tape..Thus I got my own shit..
And I know your jacked up bcuz your in school right now(lol), but for the majority of guys here Im gonna recommend that they learn to do it themselves because:
a) Only you really know what you want it to sound like and
b) you will save lotsa money doin it yourself.
I point out that Ash as far as I know isnt a professional engineer or taking his stuff to one but has some really high quality sound.Same with BigD and some other cats.
Now, if you have a budget and dont know shit about mixing then yes I say go over there and learn what its all about, Lord knows I paid attention while I was in these mud huts but I think if your gonna do production learning about the mixing process and doin hands on as much as possible is important.
Mastering? Real mastering? Let someone else do it..All day..Thats a different field entirely.
Wanna learn abut it? then buy harbal and start there.