[Closed] More DIY. Facias & soffits

How easy/hard to do?
Done everything else, but had zero experience of this. I've got a fair idea of what's required, but the thing I want to know is facia a standard size?
My current soffit sits on top of the brickwork. I know because when I replaced the windows upstairs there was no mullion? above the window frame.
So will PVC be the same size as the stuff I take off, late 60s build BTW.
And taking tiles back, is this easy?
And does the new bits of membrane go over or under the old felt?
Cheers.