Stay Nikon and use the D300. Sorry if this doesn't solve the weight issue.

2 years ago I got the D5000 and loved it. A year ago I brought the 5100 to fix my {AE-L/AF-L} focus/exposure issues. It still didn't work the way I wanted it to. Happy this year because my D800 has separate focus and exposure buttons, like your D300.

Use {i} button to enter the screen mode to change:
1) Metering mode
2) Focus mode
3) AF- Area type
4) Bracketing
What a pain, these are so hidden there isn't even a menu item for them. And you already missed photos because of the time taken to change the D5100's menu settings.

The older Nikon's use AV out. You can simulate the D5100's articulated screen on your D300 by using a stand alone hand held DVD player or TV. Or Ebay a new battery powered LCD screen for under $100. Doesn't work for the newer Nikon's because they use HDMI output.

Colin

"We don’t see things as they are, we see things as we are" - Anaïs Nin

Please visit My Nikonians gallery

/Edit: Spelling and grammar.