I ended up hiring a concrete company to cut out 6" of concrete around the entire perimeter, install drain tile and a sump pump on the other side.

If your not sure how to do it, then I would recommend hiring someone cheap to build the spreadsheet for you.

If that property passes a rigorous due diligence process and you choose to pursue it, I think, as a new investor, your best strategy is to figure out if it would be possible to buy the 2 acres with the duplexes and sell the other 8 acres.You can get up to speed on handling those or hire a PM a whole lot faster than you can figure out how to develop raw land. 

I will likely hire a property manager, at least initially, because I won't be local and available to respond to tenants' problems. 

Not saying they would win, since Muni Water districts would be ultimate defendant but landlords always get named and are forced to hire legal.

@Daniel Ryu, unfortunately, we never got to go to Korea ourselves, but we did meet with a number of country product reps, which was fun by itself. 

I was referred here by a current investor who hired me to stage a condo for her in Reston, VA. 

., should I object or just hire a lawyer for myself?

These a few things that come to mind:- Hire an attorney and CPA that are investors themselves.

I would get another eval.The company should be able to send out a supervisor tech and give another opinion.The problem with hiring another company to give an opinion is your original installer provides a warranty on the install.