if it does have external mirrors, give the brewster stems a good cleaning with methanol and optics tissue (only use optics tissue... buy some if you dont have any. anything else might scratch and will leave residue and kill power).
Also, clean the mirrors themselves using the same materials.
After that, give it a good alignment and you should be good to go. Remember, only do ONE side at a time, so when it goes back together and you need to find lasing again, you'll know it is only one mirror which is out of alignment. If you take both off at once, you'll probably need to "shoot the bore" with a HeNe or similar laser. Not a huge deal, but its much easier to just do one at a time so you dont have to worry about it.
Adjusting the mirrors themselves is easy, just adjust ONE screw at a time until the power has peaked. Try not to lose lasing while you are doing this and if you do, do not change anything else until you have lasing again. I dont know how exactly those mirrors are adjusted, but I'm guessing it's the typical three-screw setup.
