what sort of forensics are likely to be available after the firing of a Glock 17?
There's a shell casing for each round fired. In a revolver they stay in the cylinder until dumped out for reloading, in a semi-automatic and automatic they get kicked out as part of the automatic reloading - depending on the weapons and round they can kick a fair distance.
(NB: some special weapons use a caseless round, then there is no casing or gunpowder residue)
Gunpowder residue happens with most hand guns, more common with pistols as more of the residue is blown out the side between the cylinder and the barrel. However, with most semi-automatics and automatics a little is blown out the side with the ejected casing. The residue will settle on anything near it, such as hands and clothing. That's one reason why a lot of professionals put on gloves, so it doesn't get on their hands.
edit to add: some goes out the end of the barrel with or just after the bullet. If the target is close enough to the weapons when fired some of this will be embedded in the surface of the target - this is how they tell is the person was shot at very close range.
The third item is the bullet will end up somewhere, usually by hitting something or just falling to the ground after running out of energy (but that's going to be a long way away. In most cases the bullet will end up stuck in something in the direction the gun was fired - eg wall, tree, car, ground, etc. It's common for a round to miss and end up very far away, often so far away they don't find it.