Why not try an OBDII reader? I believe they had them in '98. Might just be something simple and inexpensive to fix.
Intermittent electrical issues are often a bad ground or connection somewhere. Older vehicle = more chances of bad connections. Can be time-consuming to track down. If you take it to an auto electric shop, they can find them pretty quick.
When we first got our V10 F250 a few years ago (pre-owned), we had a shop install a new battery. On the way home it went into limp mode and after being home in the driveway, could not even move it a few feet. Totally freaked out expecting thousands in repair. Got a mobile mechanic to come by and after checking for codes with his OBDII reader, found it was simply a connector near the battery that had a crack in it causing a bad connection. He just wrapped tape around it and it's been fine ever since - only charged $60. I bought an OBDII reader after that and keep it in the truck just in case. Have used it on two of our cars too and has been a good investment (under $100 @ HF).
DW got a new car (1 year old lease return) recently. One day a bunch of lights on the dash were flashing like crazy. Use our reader which showed a massive engine air leak somewhere. Lovely. Finally figured out it was because the gas cap was not tightened down. Doh... Had to use the internet to pinpoint the cause as the reader alone is not always enough.
