(yes, edit out your personal details!)
I'm sorry for your loss.
afaik, unless he specifically put aside assets in a separate trust, the bulk of your father's estate will probably have to go through probate court to ensure there are not any outstanding creditors wanting a piece of his estate. An estate attorney who handles only these types of cases will help with the details and make the process smoother. You might be able to get leads from family planners, friends, etc. Ask around.
With Roth IRAs you pay the taxes up front for long-term investing. The stock market still hasn't hit bottom yet so that is something to consider in turning cash into investment. The rule of thumb I've heard (Suzy Ormand?) is to stay diversified and have 1/3 cash. 1/3 stock, 1/3rd bonds or other.