The crank: Kinda depends on how mutch your willing to spend. If your on a budget then dont worry about it. But if you have the money and want to do it right, have it balanced. It will even things out and help it run smoother. A correct balance job includes the rods and pistons you intend to use, as they all get weight matched. As for price, it will kinda vary from shop to shop. I had my 401 balanced and although I cant remember, I am thinking it was somewhere around a couple hundred or less. Its been so long ago.
As for the rods: I wouldnt risk it and try doing it yourself. I would take it to the machiene shop and let them do it. Most shops wont charge too mutch for that.
'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch. Currently building a stroker.
'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.