You can work around a faulty shift interlock by:
1) Turn ignition key forward to the position between LOCK and RUN
2) Shift the transmission into NEUTRAL (Engage parking barake first)
3) Start engine
4) Shift into gear avoiding PARK
There is also a mechanical bypass method listed on page 131 of your owners manual. If you don't have one, go to
www.fleet.ford.com and download it from the Maintenance section. They have guides available from 1996 on.
Suggest you have your charging system and battery checked out.
Steve