Is my Dad in a safe place even if he didn't go to church and drank a lot?
I'm sorry to read about your Dad's death. I'm sure this has been a difficult time for you. Your question of whether there is life after death is certainly an important one and one that people have grappled with over the years. It is also one of those questions that is informed greatly by one's own spiritual and faith beliefs. I don't know if you gave any thought to these questions prior to your Dad's death but, depending upon your belief (faith) system, it certainly is easier to deal with it before a death than after a death.
I don't know what your spiritual background is, and I certainly cannot force mine upon you, but I strongly believe that there is life after death. From my perspective as a Christian, this belief is based upon a commitment I have made. Now, if your religious background is something other than Christian, or if you have no spiritual/religious background, your outlook may be different.
Even if you haven't thought about these things prior to your Dad's death, I think it is important that you do so now. I would encourage you to do some reading or spend some time with a clergyperson and ask them about some of these issues. The key thing is that you explore this for yourself so that you know what you believe and have a rationale for doing so. It took your Dad's death to get you thinking about these important life questions, but there are other people in your life (including yourself) for whom this question will be very important at some time in the future. It is very wise to develop your own beliefs about this so that when death occurs you have an important framework from which to view it.