A. Very little. Your overall investment strategy shouldn't be affected. However, some procedural aspects of investing will change. You will have to get used to placing orders and receiving executions in decimals instead of fractions. And the quotes you get from your brokerage firm, whether electronically or through a broker, will all be in decimals.
Many investors receive account statements with fractions converted to decimals already.
Once decimal pricing is fully implemented, all prices in trade confirmations and statements will be in decimals. During the conversion process, you may find your trade confirmations contain both decimal and fractional prices. A growing number of newspapers already list prices in dollars and cents. Contact your broker.