Here's another vote for a professional guide, and Siam Roads seems to fit the bill (I have no personal experience of their cervix) I've only spent a couple of days in Bangkok with my little friend from Si Saket. He's never been before, so wasn't terribly useful as a guide. The floating market we went to was a total tourist trap, though I was impressed with the Grand Palace. But we got lost after that and had to take a taxi back to the river.
So an experienced guide would be well worth the money, and from what I've seen of the website, the fees are very reasonable. So get onto Moses and get a guyide sorted.