There is the easy way - find a copy of stace's Win98 image before he had to pull it due to MS pressure. Surely, someone here downloaded it, and could be induced into parting with it privately.
Then, there is the hard way. It involves a CF/IDE adapter that will allow you to install the drive into a normal PC. Install the usual way, save you need to boot into "safe mode" before the last stage and kill the ACPI options. Once you have a base install working (with the VGA driver, no sound/CD-ROM/modem etc), move the drive over to the IA-1. There is info on how to do that elsewhere on the board. Drivers are another issue, but I (and probably many others here) can set you up with the drivers you will need.
Be forewarned, Win98 will be a bit twitchy on the IA-1 due to the lack of DMA access to the microdrive. I found it usable, but irritating.