It is scary and I would allow a morning if it is your first time. On the 3020 the last mirror did/does not have any adjustment other than shimming it with thin card/paper.
There should be instructions that came with the machine, the idea is to get the beam to enter roughly in the centre of the hole in the head before the last mirror. I would take the last mirror out, place a bit of tape over the hole and text fire in all four corners (on a new bit of tape each time) this will give you an idea if it is out of alignment if the burn mark is moving. If it is not it could be the last mirror needs shimming so do the same (with the mirror back in place) but put tape over the exit hole of the nozzle.
Removing the mirror stops it getting smut from the test burns