3 y/o drill lost power while applying excess force on screw. Smelled something wrong. Would not perform properly afterwards (very slow speed). It worked (spun briefly) OK 1/2 hr later but w/ blue/green sparks inside motor. Battery OK. Did I permanently damage the drill? Would I cause anymore damage trying to use it? Left it alone.

Sparking is an indication that the brushes have to be replaced. Unknown if you did any more damage. Exact model #?

Model # P206

The parts breakdown diagram is here: http://www.ereplacementparts.com/ryobi-p206-18v-2speed-drilldriver-parts-c-7931_8051_8064.html

The motor is available for about $25 not including postage.

Brushes don't appear to available separately.

Assuming you didn't damage the gearbox or the switch it's probably not a bad repair.

Thanks, I'll let you know.