Back to the OP's question and concerns.

Win98 is going EOL at Microsoft. SO WHAT!!!!!

If it still works fine with all you need this computer to do, keep on
using it as long as it lasts, even spend little bits of money to replace
things if they break (power supply, mouse, keyboard, monitor) Shop
around, used items, especially for monitors can be quite good and quite
cheap. Power supplies, Rodents, and Keyboards are cheap.

When it breaks big time, i.e. hard drive fails, processor fails, burns
up...... Then go see what the market is offering and make your decision.

Right now, if you go buy a machine from Dell, HP/Compaq,e-machines,
Sony..... they call come with WinXp (home or Pro). In 6 months to a
year, they will all come with Vista.

End of Life is a meaningless term. All it means is that if you call
Microsoft Support, they will refuse to answer your questions. If you
find a bug (bloody unlikely), they will accept your information, but
nothing will ever happen. EOL does NOT mean that Win98 will STOP
working, that the machine will refuse to boot Win98. Far from it.

IBM stopped supporting OS/2 several years ago. There are tens of
thousands of computers around the world (even ATMs, bank teller
terminals, stock brokerage terminals) that are still going strong with
that old product. Just don't call IBM for support issues with OS/2,
you'll get no answers.

EOL does not mean that the product stops working, it just means you are
on your own for support (and most of us are in exactly that shape
regardless of whether we use something from Microsoft, a Linux version,
OS/2, Apple........)