$330 is about what you would expect to pay, to have a shop do it, however ring a few mobile tinters, and you should find it's a lot cheaper..I had mine done for $220, i think it was, but some are as low as $160-180...As far as darkness level, i went for 5%, i would never pay for that 35%legal crap, it's about as useful as flipping down your sun visor..5% is good, pretty dark at night, but you get used to it pretty quick.. If your really keen to go super dark, some places make a 2% tint...
And there's different types of film too obviously, i went for the metal film, but i dont really think it suits, i think the dye based film, suits older cars better, and the metal tint being more suited to a modern car....Anyways that's just my opinion, i'll try and throw up a picture of what my tint looks like..