1999 Jeep Laredo How do I reset the Diagnostic system. Plea

OK, 1999 JGCL had a Speed sensor output that went bad CODES P 0320 0720. I replaced it with a brand new one. The problem was solved. A couple weeks later I used a hardware store key that started the Jeep, but it shut off soon after starting. This gave me the P 1685 code for invalid SKIM key. Now about two weeks later the Jeep sometimes starts/revs up fine and drives, but then it dies and won't restart. After sitting overnight it started again and drove about 3 miles then died. NOW it turns over but will not start at all. WHAT I THINK: Fuel Filter or Fuel Pump. However diagnostics 3-turn key on board RESULTS say the same codes as before and nothing about FUEL FILTER or FUEL PUMP. Could the JEEP still think the KEY is invalid even though we are using the STANDARD stock CHRYSLER KEY? The codes is still there along with the Speed sensor codes? Please help. ALSO: How do I reset the codes so they go away?