Answers to your questions...
1. Constant run through isn't a good thing. It bring in foreign species and takes nutrients out. If you could do it without the constant run through, it would be better. My site is at the juncture of 5 wet weather creek beds. The difference is that the water doesn't constantly run through my creeks.
2 and 3. Put the pond where the land will let you. Look at a topo map or post one here and there will be about 6 people telling you where it should go and how big a pond you could do in a day or two.
4. I am tempted to try and do mine myself. I could do it for about half the cost, but the big question is whether or not I could do it right the first time. Digging a pond is a true mixture of art and science. There are dozer operators who build roads all day long that I wouldn't trust with my pond. If you don't build the dam right, slope the sides right, seal the bottom and sides with enough clay, etc. it ends up being a $10,000 mud hole that breeds mosquitos and no fish. Being in North Texas, call Mike Otto at Otto's Dirt Service. He is tops in the business, and he is one of the main contributors to this site. If he is too busy, I am sure he can recommend somebody in the area. Here is his website:
http://ottosdirtservice.com/default.aspxI was going to get him to do my place, but I couldn't afford the transportation costs and putting his crew in a hotel for a couple of weeks. If you can get him to do yours, I am very envious.
