If I sourced a new hard drive its relatively straight forward to fit? I.e lift keyboard unplug/plug in?
I’ve done a few of them, nothing that hard but it’s a long and fiddly job that involves a pretty comprehensive strip down. Keep the screws you remove separated as there’s several different lengths and threads used.
Drive will be less than £50 (remember IDE not SATA) so wouldn’t cost a great deal to do. 512MB memory modules are £15 from Crucial, so could get 1GB in there quite cheaply too.
Not that it stops it being an old, slow machine that can only run obsolete versions of MacOS. I’d probably fix the hard disk just so you can sell a working machine rather than a “spares or repair” one but if you’re looking at paying someone to fix it for you, I’d say sell it as-is.