You should be able to do a clean install with an upgrade CD. It will ask you to put your 98 CD in the drive to verify that you have actually got a 98 licence. The XP CD will come with all drivers that have been updated to XP as at the date it was produced, so you should have minimal driver downloads.
If you are concerned, and you have the disk space, why not create a partition (say 10Gb) and install XP on that giving you a dual boot PC until you have tested everything runs as you want under XP. The setup routine should ask you to choose a location for the install (choose D:) and will set up the multi boot facility automatically.