The main websites linked to above are also in English - so take a look. The A25 motorway to Rome lies between the two parks, and Tocco is on the side of the Maiella. To find Gran Sasso, just cross the motorway at Torre de Passeri or Popoli and head upwards into the mountains.
Favourite places in Maiella
Pescosansonesco - there is a largely abandoned ancient village above a newer village. Between the two is a huge cave in the hillside. It's a very short drive from Tocco - just head into Torre de Passeri (the town by the motorway exit for Casauria) and you'll see signs.
Favourite places in Gran Sasso
Rocca Calascio - a partially restored castle with incredible panoramic views. You'll need a map or satnav for this one - but head in the direction of Popoli and then into Gran Sasso. You can drive almost to the top of the hill and have a short steep walk to the top - or park at various points up the hill for a bit more exercise. The views are spectacular in every direction.