Like others said, sheep ain't low maintenance.   They need attention, although I doubt a little work ever killed anyone.

The wet ground will be a problem if there is mud.  If you mean it is wet in the early spring and dries out by the time the sheep would go in, then it would work fine.  I'd say go for it if it dries out enough.  Just be prepared for the unexpected, like the sheep figuring out how to get out of the fence, or someone getting their head stuck in the woven wire.

Also, how's the drinking water situation?  It's hard to get sheep to drink from anything but a tank or a fountain, and then it has to be dry where they stand.