Using gimp for digital photo scratch repair

[Vaughn Treude]

The title pretty much says it.  Can anybody point me to a good how-to
guide for this purpose?  I've found references that say the Gimp can do
this but no good explanations yet.  (In my particular case the problem
is actually not a scratch but a wire-like object across the field of
view.  It's a bit wider than a scratch would be but I'm hoping there's
some way I can trace the "scratch" and have the program merge in the
surrounding colors.)

Thanks!
Vaughn