the only nurses i know that actually intubate are the advanced practice nurse anesthetists. nurses who take acls training learn how to intubate, but i've never heard of them actually ever doing it on real patients since most nurse practice acts don't permit it.
as for n/g tubes. . .you bet. i'm guessing i've put hundreds in over my 30-year career because i've worked a lot of med/surg. i've also re-inserted trach tubes, inserted foley catheters in both males and females, inserted rectal tubes, suctioned both orally and nasotracheally, irrigated ears, eyes and noses as well as all kinds of open wounds, and i was trained to inserted p.i.c.c. (peripherally inserted central catheter) lines which is a specialized iv technique and suture them in place. i've assisted doctors as they were inserting endotracheal tubes, chest tubes, tracheostomies, bone marrow biopsies, liver needle biopsies, central line insertions, cutdowns, and female gyn exams. i'm sure there's been more, but these are what come to mind at the moment.