Death is death. Your asking implies the possibility that 'something' is alive ... survives death.
Disembodied spirits can scare us and maybe harm us too in a psychological or negative way. As to the other part of the question, Soul's eventually go to the Souls world and is subjected to the Will of the Supreme, like God-souls are.
They can and do help us, if it has been sanctioned, approved or tolerated by the Supreme, The Absolute. Are they aware? They can be. Some Souls have very, very close connection to their loved ones.
You can also invoke them. Earth is a dense and dark place in terms of evolution, and Souls will have to suffer to come to you. Spiritual energies are higher... finer...subtler...
Ultimately, all can be done with the Presence of the right Master and the Will or Sanction of the Supreme. Finally, you should know that good Spirits will tell you what your inner voice is telling you all the time, or scriptures say in different ways.
If you do not gel with one, then seek another. There are many! As a guideline, let go of anything that makes you weak; does not bring inner Joy or abundant Peace. Conscience tells us if we listen. Practice Silence, as this will make the inner voice more audible for you, post calming the restless mind, a major source of all ails.