Little Dog--
Doing it yourself would be tremendous if it worked out--what an achievement! Then again, there are few things sadder than seeing a piece of equipment abandoned in the middle of a project with morning glory vines and ironweed growing up through the tracks and big swales cut through the dirt by the runoff. There also is a level of personal risk which has to be taken into account; people do have accidents while driving heavy equipment up and down steep slopes. There is the value of time: Having a pond filling up with water in three weeks might be as rewarding as doing it yourself in six months' time. And there is the value of a warranty and someone else's insurance policy: If something bad happens, you're not in it alone.
A few things come to mind based on our experience. First, the fellow who put in our pond grew up using just dozers to build ponds (starting when he was 12!), and now that he's taken over his uncle's company, he uses a dozer and a trackhoe, which he believes cuts his time by about 60%. For example, what will you do with 1,000 stumps? He dug a 20'-deep hole with his hoe, dropped/pushed all the stumps into it layering clay as he went, and compacted dirt over the top. How will you cut your dam keyway? The hoe did it in hours. Then, there are issues like if you hit bedrock, do you seal it off, and how? Finally, somebody who's done it a bunch is more likely to hit an aesthetic bullseye with things like grade, shoreline, etc., simply by virtue of experience.
Anyway, if you decide to go it alone, what about establishing a relationship with a pond contractor before you start, getting him to agree to consult with you on a daily/weekly or whatever basis for an hourly rate, and then having him tapped to come in and bail things out if things start to get sideways, and/or to come in and actually handle critical junctures like clay compaction, sealing rock layers, etc.?
