My father never opened succession to my sister or I when my mother died this year. We waited 6 months for him to open succession, but never did. He secretly got married in another country and we found out. He was and is pawning my mother's jewelry and other of her personal possessions. He will not allow us in the house to retrieve her items.
My sister and I opened an instate succession, not knowing if my mother had a will or not. We got the judgement of possession and now my father wants to buy my sister and me out. My question to you is can he put an injuction of the judgement of possession? The notice was in the news paper and is it my sister's and I's responsibility to retain an attorney to amend the settlement? What is the next step since now my father wants to negotiate?

This is a world site. If you are in the US state of LA, and by 'instate' you mean 'intestate,' please let us know.

I won't pretend to know LA laws, nor am I a lawyer (there is one who is here most days).
LA is unique among the 50 states regarding inheritance law.
If you want to do this on your own (no one HAS to hire a lawyer), I would still consult an attorney local to the estate, either very briefly for free over the phone, or for a set amount of time for a flat fee. Your father has the upper hand in so many ways, by virtue of holding your mother's property. I assume that it isn't going to be easy to provide an inventory of her possessions other than real estate.

Also - have you talked with the Clerk of the Court? If they have been there for years, they know as much as anyone about the steps to take. At least to add to your knowledge before you pay a fee by the minute.

As noted, any question on law needs to include your general locales as laws very by area. This is especially true of laws of inheritance.

However, generally, anyone can appeal a judgment of any kind. You don't say whether he appeared at the hearing, but the fact you had to publish notice of the judgment in the local paper indicates he wasn't. This gives him more ammunition to ask for a stay of the order until he can appeal.

Assuming your mother dies intestate (you really need to make sure of the spelling of the terms you use) you may or may not be entitled to a share of her estate. I would guess that you are since the court issued an order.

As for the settlement He can buy you out if you want to let him, but first I would demand a full accounting and valuation of the estate.

... is it my sister's and I's responsibility to retain an attorney to amend the settlement? ...

(FYI: it's "my sister's and my responsibility... ". If your sister wasn't in the sentence, would you ask "is it I's responsibility?")

I don't see how you managed to get a judgment without an attorney, but evidently you did. If your father wants to settle, insist that he pay you a reasonable attorney's fee to draft (or at least review) the settlement, and get it approved by the court.

Yes, esp if he was not present at the hearing for judgement, he can appeal and get an injunction till another hearing, That would not be uncommon at all.