For reasons I won't get into I ended up going to many post mortems as a medical student.
The reassuring thing is that the bodies are treated very carefully and with respect, they are for example washed carefully. Everything is done by the book and with the utmost care and thoroughness. Which is of course as it should be because the pathologist is fulfilling a legal duty.
However, the methodical thoroughness is in its own way disturbing, because essentially it is very invasive and I recall that I did feel more disturbed about the prospect of eg my own relative having a post mortem after I had witnessed them first hand (although I don't feel this way any more so maybe I have become a bit more hardened since my medical student days). The process of carrying out a post mortem is implied in the detail of the report and that may be very difficult to read about. Also, sometimes a very stark picture of the circumstances of death is created, and at other times, it's much more vague - each could be upsetting in different ways.
Edit: It sounds like a strange thing to say but a post mortem really hammers home in a brutal way the reality that a person is dead and what is left is their dead body. I suppose reading about it in detail could have the same effect. I think some people might find that helpful and others would find it too-much and that might depend on where they are in their journey of grief and their own individual perspective / approach to things.
If I were in your position I would not be able to resist obtaining a copy of the report but what I think would be ideal would be for someone you trust (ideally somebody who is in the medical field but failing that someone sensible without an emotional connection to your father) to read it over for you first, as that may help you to answer relevant questions before you make your decision. Eg: are there photos (and if so could these be removed or blanked out), does the description of injuries give a vivid impression of how your father died, what was the general condition of your father's body and so on.
I'm very sorry for your loss and I hope I have managed to word this in a way which is helpful.
I also agree that it is entirely appropriate to visit your GP in relation to a bereavement and most GPs I imagine would be very happy to discuss the post mortem with you if this would be helpful.