1998 Ford Windstar with code P0358:Ignition Coil H Primary/S

1998
Ford
Windstar (Limited)
3.8L

Getting OBD II fault code P0358 Ignition Coil H Primary/Secondary Circuit Malfunction

I am about to do some travelling and this has just popped up. How critical a potential problem might this be ?
Should I get a spare ignition coil (just in case) ?

Looking for advice and suggestions on this one.

Steve

I have a 1998 Ford Windstar 3.8L

Experiencing turn signal problems:
1. started off having left side not working, then it would come back.
No audible blinking sound or visual flashing light indication on the
dashboard.
2. normally the right side was okay but occasionally it would also
fail (not blink), although usually the left it was neevr both at the
same time.
3. checked all fuses and bulbs - good. Replaced flasher with new one
and system appeared to be back online.
4. started to hear buzzing sound when trying to go left - no left
signal but right works.
5. finally - both sides failed outright

> possible multifunction switch fault now ???

looking for your advice on what to do next. New switch is +$100, would
like to verify if I need that before buying (most shops won't accept
returns on electrical parts)