50' is about 2 1/2 minutes (at 24fps). You can extend it to roughly 3 1/3 by changing to 18fps.
You may as well buy your film direct from Kodak. You won't end up with old/dated filmstock, and odds are if you buy anywhere else they'll have had to mark it up a bit, anyway.
Make sure you decide where you'll be having your film developed & transfered, besfore shooting.
Yake Film & Video (linked above) are very good (nice people, too). They no longer process Colour-Negative S8, though. Even if I get film developed elsewhere, it always ends up at Yale for the transfer to mini-DV.
Shooting in colour, you can either use the Colour Reversal (Ektachrome, atm) or Colour Negative. All have their benefits. You should look 'em up.
Make sure all your ducks are lined up, before starting. It's not really that tricky (the order in which things get done), but it can be a little overwhelming initially. All kinds of things to keep in mind.
Oh yah, read up on how/why/when to use the daylight-filter built into your camera.
Have fun with it. Same camera as mine, if it's the AZ.