Firstly, I am not an expert in tree pruning (or anything else) so if it goes wrong don't blame me!
I know that you can prune "Christmas Trees" (I assume that it is a Norwegian Spruce) as they prune all the christmas trees growing in the fields around here to make them more bushy.
Also my dad has one growing in his garden - they have lived there for over 40 years and the tree was there well before them. The top died, probably about 1975, when the tree would have been 15 to 20 feet high, so dad simply cut the dead bit off the top (10 ft or so). The tree is still going strong, one of the side branches just turned upwards to become the new "trunk", and the only way you can tell now is that the tree has a slight kink in the trunk part way up.
So, it is unlikely to kill it if you cut the top out to reduce the height and cut back the side branches, and it sounds like you don't have anything to lose as it will just continue to grow if you do nothing. Probably best to cut the top back to just above a set of side branches, and prune any side branches back to buds on their stems. It will look a bit odd when you first do it, but should re-grow OK, and cut it back to a bit less than your ideal size to give it some growing room.
