Indigo 1 is slightly mistaken. Patches and fixes for W98 will be available on hundreds of site for yonks. Interestingly I had W98 for 5 years and never downloaded any patches or 'fixes', i did not shrivel and die...if it ain't broke don't fix it.
Yes if you have the upgrade disc you can just put it in the drive and away you go. You can even have Win95 up and running when you put the CD in and it will do all it needs to. As with anything, back up your work first...but then everyone does that on a regular basis anyway don't they ;)
As for patches, I'm sure you'll be able to get hold of ones you need. Most will seem to make little difference, but there are some that do...and not just security ones either.
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