Hi,

Having repaired power tools for many years, it is probably not the
brushes - it is far far more likely that the drill is burnt out
(insulation between the windings has broken down due to excessive heat)
It takes a lot of use to wear brushes down but it does happen.

If you need to compress the springs to get the brushes into place then
it isn't the brushes.

That said, brushes are pretty cheap and worth a try. You should be able
to get them from your local friendly power tool sales/repair place. In
fact, if you took it in to them they should be able to tell you within
2 seconds of plugging it in what the problem is.

A dirty commutator is also possible but unlikely. Cleaning it with a
little light emery paper and gently cleaning out between the segments
is an easy task.

It could also be sticky brushes where crud prevents the brush from
moving freely in its holder and therefore from properly touching the
commutator - do the brushes move in and out freely? If not, clean them
and the holders.

Let us know how you get on.
(my fingers are crossed for you that it is something cheap)

Alan.