If you're comfortable with that camera, get it!

Don't forget that sound is 50% of the movie watching experience. You want a
good shotgun mic. That in itself is a generic term that means any long barreled
mic. You want a good condenser (externally powered) mic with a “lobar” pick up
pattern to put on your boom pole. Lobar pick up means the mic focuses its audio
pick up to a narrow area. This is why you want to use a boom pole to get the
mic as close the the actor as possible - you’ll get clean dialogue tracks with less
ambient noise.

http://www.sennheiserusa.com/newsite/
Sennheiser is the mic most used by professional sound recordists. They are
expensive and worth it. Check out the ME-66 and the ME-67. The MKH60 is
the best if you can afford it.

http://www.audio-technica.com/
Audio-Technica is cheaper. Check out the AT835B. It’s a workable mic, a little
muddy and not as directional as it should be. The AT835ST is a good mic for
the price, but it, too, sounds a bit muddy - the vocals don’t sound crisp
enough for me.

http://www.azdencorp.com/
I’ve never used Azden mic’s. They’re inexpensive and I don’t hear too many
good things about them, but if that's all you can afford it's MUCH better than
using the camera mic.

http://www.rodemic.com/?pagename=Home
Rode is an inexpensive mic - it’s okay for recording instruments but their
shotgun mic’s aren’t very versatile.

A good mic is an investment. It will last longer than your camera - why skimp?
A great place to check prices and purchase is B&H Photo
http://www.bhphotovideo.com/

The further away the mic is from the actors, the higher the volume needs to be.
The higher the volume, the more “noise” you get. Your goal is to have a very
high signal to noise ratio - more signal (the dialogue) less noise (the background).
Even a very good, expensive Sennheiser mounted on the camera will pick up
a lot of background ambiance because it’s far away from the actors.

So you need a boom pole. This can be as simple as a painters pole with a microphone
shock mount on it - or a 3 or 4 section, expandable Carbon Fiber, Graphite Fiber
or Aluminum boom pole. The lighter the pole the better. Expandable is also very
convenient. A pole that’s a fixed six or eight feet (painters pole) can pose problems
if you’re shooting in a small space like a bathroom or small apartment or if the
boom operator needs to be twelve to fifteen feet away to be out the the lights.

A good Graphite, five section boom will be light, range from two feet to nine feet
and cost $500 or so. A pro boom-op will invest in a good pole. No need to spend
that kind of money if you’re making one or two shorts a year.

Lighting is also very important. Just because you're getting an image on the screen
doesn't mean it's a good, professional looking image. It's amazing what a little fill
and backlight can do to make your movie look more professional.

Regarding the computer: if you're a Mac user you already have a very powerful
(and free!) editing software installed. Final Cut is the next step up. If you're not
on a Mac I can't help - I don't know anything about PC's.