You should be able to shoot lead bullets in a Glock, I'd just make sure they are hard and not pure lead. I shoot Oregon Trail bullets, they seem pretty hard and I have not noticed any leading in any of my guns.
Some people have postulated a relationship between the use of cast lead bullets and gun blowing up, arguing that buildup of lead in the chamber can lead to pressure buildups as well. The jury seems to be out on this one as a direct causation, but lead build-up will sometimes cause a round to not fully chamber, and as Glocks can discharge with the action not completely locked up ("out of battery," this can lead to a catastrophic failure.
Some suggestions to avoid having a gun fail on you are install a custom barrel (with a supported chamber), inspect your brass, load "hot loads" only in new brass, don't use range pickups, don't shoot "hot loads" from used brass and discard used brass sooner than you would normally.
Use calipers or case gauges to keep your reloads within spec. Check for excessive bulging in the case web and make sure your bullets are seated to the correct length. Also check for excessive case thinning or bulging.
There is a ton of info on the net about this subject. Glocks are frequently mentioned, probably because there are so many of them out there.