In my book, no.
As far as doing it without a lawyer or a will, I used a lawyer for my dad's estate, which was fortunately structured as to not require a will. We did a "quit claim deed" on some clear title property, signed over the title on his old truck and his bank account had my name on it. The only thing left on the table were some utility deposits that I couldn't claim, but they were less than what a will and probate would've cost.
You might need to make sure you and your sis aren't going to get stuck with his debt though.
