The NRT flight will definitely come into Terminal A - the customs/immigration area is below Gate A38 or so.

Unfortunatley, you are arriving during a busy time as this is when a lot of the Europe flights arrive.

However, i have to say i have cleared customs and immigration at DFW many times and it is very well run and very efficient.

You will need to claim and recheck any checked luggage to your final destination (if you checked anything in NRT).

After doing this, you will need to go thru security to re-enter gate area.
If your flight is NOT departing out of Term. A, you may wish to take the TRAAIN from Term. A to whatever Term. your flight will be departing from (most likely C). the trains run every 2 minutes.

Assuming your domestic flight departs fropm Term. A, you will have plenty of time.

I would definitely (while waiting for any checked luggage) double-check the monitors for any gate changes.

I know the 777 (NRT-DFW plane) will display connecting flight info. - so this should help you develop a game plan while on final approach into DFW.

I hope this helps.

Good Luck.