In case anyone needed, here's a Mac-compatible USB 3.0 card that works in the older Mac towers:http://www.bhphotovideo.com/c/product/1143180-REG. Given some upgrades, the legacy towers can be a powerhouse with this device.
I honestly don't know if the D7000 will output anything over 480p on a field monitor. MAYBE 720p, but B&H does not state. As for a microphone, you can definitely get one to combine as a package, but I would not hook directly into the camera. I would have an external audio device handling sound. Use the D7000 for reference audio. But again, a field monitor would really only help with focus and framing most likely.
In addition to the other comments, I've always felt that you are what you do. I would just start or continue shooting films, whether that's finding directors who already have a script, or making your own films. Just never stop shooting and always improve your reel. Soon enough the free work that you do will be seen as valuable to someone else. Until you're able to support yourself just as a DP, you'll probably have to get a day job to support your projects/gear for a while.
I upgraded from the Canon 7D to the Canon C100. Love it and use the 7D for stills.
A cinematographer does several things before hitting that 'record' button. He/She has endless discussions and meetings with the director on shots. He/She may even do a location scout. From there, he can work with the director on a shot list. What is captured should always be a collaborative effort. Being the DP, it's default that you will add your own creative wisdom on how to achieve the director's vision. I've seen detailed and basic shot lists. However you decide to make yours, make sure you include: lens, wide/medium/close-up (if not more detailed), movement, INT/EXT, day/night, and general action. All of those will determine how the shot is executed and seen. They should all have reasons for existing.
After having meetings/discussions with the director, I've often made my own shot list (to get started) and presented to the director. From there, he/she can see my gears in motion and we can fine tune a shot list.
Granted, you may do some shots on the fly as shooting may not go 100% smooth on set and a million other things can interfere with your schedule/shot list. However, because you've had so many discussions with the director about his/her vision, you should be able to come up with alternative shots that will tell his/her story. You should NEVER work blindfolded when working as a DP. ALWAYS have some clue as to what you want to do. Not being even a little prepared will not yield positive results.
Where can you buy the attachment?