Disagree on the trencher.
A 6" wide chain on a trencher will allow you to install a 4" drain pipe.
Really not that hard, and you still can do a French drain if you wish also.
I do agree though that a good soil analysis is in order to figure out why there is a water issue, especially on top of the hill.
Has this HO had water issues in the past or is this the first sign of problems?