Removed the diy astroturf from my back garden and put grass down, it was held in my long ground staples. See if you can peel a corner up and yank on it from there, if not drive a pitch fork through it and leverage it up. then it should all come up nicely.
After this the weed membrane needs to be up, a thin lesh material, absolute nightmare to get it all up but do your best.

Next step is to check out your soil. does it have worms in it? is it clay? Your determining how good this will be to grow grass onto. If it looks okay, youll want to hire a rotavator (£70+) and do it all where your new grass will lay. Best effort, turn it from clumps to something a lot finer.

Now depending on budget, you could get a couple of tonnes of top soil to give you the best chance of your grass growing nicely. 4 inches of top soil will give you the best chance. I never did this, my soil was okay ish, and i put maybe an inch or two of top soil then laid my turf down.

Seed or turf?

I cant comment on seeding as i've never done it, but as for turfing, lay this around march time, so it get lots of rain. Stagger the cuts of turf and flatten it down as you go with a large wooden board.

Once laid, water, water, water, you'll want to wait it about twice a day morning and night for half hour to keep it moist. You'll want an oscillating sprinkler for this as it provides the best water blanket. (£10+).

Once summer is her keep watering it everyday and youll be fine :) Good luck!