According to the Old Testament, the northern star is Heaven, and according to am NDE story, the Hellish place is near it.
which star is closest to the north pole varies ...
The precession of the Earth's axis has a number of observable effects. First, the positions of the south and north celestial poles appear to move in circles against the space-fixed backdrop of stars, completing one circuit in 25,772 Julian years (2000 rate). Thus, while today the star Polaris lies approximately at the north celestial pole, this will change over time, and other stars will become the "north star"http://en.wikipedia.org/wiki/Axial_precession_%28astronomy%29
Does that mean that from time to time, Heaven and Hell are reversed as the Northern star changes to another nearby star?
As for as the other questions, yes, it is in the Milky-Way. Yes, it does still exist (you can find the North Star by finding the Big Dipper, and sighting along the two furthest stars in the pan, and looking for the brightest star in that line. That is assuming you are in the Northern Hemisphere. Those living in the southern hemisphere wouldn't be able to see the northern star.
According to Wikipedia (above), it is not just one star, but actually several stars. However, there is no mention of planets.
Polaris A is a supergiant star, which means that while it is larger than our sun, it will burn-out and explode as a supernova long before our sun eventually burns out.
If you could travel at the speed of light, it would take 434 years to get to Polaris. At slower speeds, it would take much longer. That also means that what we see there today is already 434 years old.