Of course the answer to the question, "undecided whether to take the Dealer trade or sell my car myself?" Depends on how much the dealer is offering for the trade-in.
Here's what I have done in the past. I had a 2007 Rav4 that I wanted to use to trade for a newer vehicle.
So, I went on line to Edmunds:
http://www.edmunds.com/appraisal/ and got a price for what a dealer would sell the trade-in for and I chopped 2K off of that number. Next I told the dealer the number I wanted for my Rav4 in a trade and he offered me 2K less than that number. So, I walked out on the deal. Two days later he called me back and offered me an additional 1K for the trade and I told him it had to be yet another 1K. He said they could not do it and that was the end of that conversation. The next day he called back and I got my full asking price for my trade-in and we did the deal.
The point is that you need to know what your car will bring to them and allow for them to make a profit on it and stand firm. Good luck!