Remove and replace door frames

[Burro]

Hello, I am refurbishing the whole kitchen and doors and door frames (1930ish) must go.
I've had the frame stripped to make space for a plastering job
The arch inside the wall is still there, can I remove that with no collapsing consequences?
How easy is it to fit them myself
What is the best frame I can buy?
Where can I buy them?

Thanks
Burro

 

[JohnD]

arch

show us a pic

a house of that age may have no lintel, they often built the bricks onto door and window frames