A friend of my fathers passed away in the 90's, leaving behind a storage unit full of stuff that sat unopened in our garage for the past decade.Finally decided to go through the stuff and hit the jackpot: a sig pistol, ruger .22 and a few rifles. Now they are in California, I am in Nevada. No paperwork whatsoever for them, also no family members to pass them onto. What, if anything is necessary could I do to legally take these?
The answer to the question at the end of your post is probably nothing. Technically, by the letter of the law, you've been illegally in possession of the guns for the past decade anyway.
18 USC 922 (a)(3) and (a)(5) prohibit the transfer of firearms across state lines with exceptions for intestate succession or bequests.
Intestate succession is when a person dies and their estate passes to their heirs without a will in accordance to state law. As this "friend of your father" is not related to you, I doubt California law would consider you to be the heirs of the estate.
Bequest means there was a will and you would have to be named in the will to receive the guns.
It does not appear as if you would meet either exception to the Federal law. You say there is no family left, so who could be considered to be the current legal owner of the guns for an FFL to receive them from in order to transfer them to you? The FFL must log guns in, and who they came from, in order to transfer them out.
The reality of the situation is that at this point, nobody official cares - not the FBI, ATF, NCIS, CSI, SVU, etc. Keep the guns and do what you want with them.
If you were named in a will to receive the estate, and the stuff in your garage was part of that estate, then you have already fulfilled all the legal requirements to obtain the guns.