1) you are not supposed to no. However, IF you do clean it real good every 100 rounds or so and it should be ok. SHOULD.
2) Not that I am aware of no.
3) Go to the handgun section and look at the sticky posted by BIG BORE for LEM instructions. You will actually have to look inside of the pistol to answer your question. All the info you need is there though.
By the way nice deal on a used HK congrats.