The maintenance disk was simply a floppy with rewritten code on the first few sectors that bypassed any kind of checksum or self-diagnostic. Useful if you lost or forgot your BIOS password. Also let the tech into the bios to look at settings before replacing the chip. Back then it was cost effective. Nowadays they just replace the whole dang shebang.
Here are your main options, in order of attempt:
1. Hold down esc key when booting, see if you can get into bios. If not...
2. Remove battery and disconnect ac adapter
3. Gently disassemble case until you find a round coin-like battery
4. Go out, buy replacement battery, replace battery, then reverse step 3 and 2
If these steps fail, you've a bad BIOS chip, you could try to ...
5. ebay it.