Yes, it is worth having some instruction if you've only trained on hard runways.
Things that are different about grass runways:
- braking distances can be very variable, depending on how wet or dry the grass is
- takeoff acceleration can be impacted by the length of the grass
- it can be hard to see the runways if the length of the grass has been allowed to allowd to get too close to that of the surrounding area
- the perspective of the runway on approach can seem different (but it isn't really)
- grass runways often have many less markings compared to their paved counterparts, centre lines, numbers.
- Airfields with grass runways often also have grass taxiways that can be more difficult to see.
- Airfields with grass runways can be hard to see period!
You should definitely plan to come to Derby and also go to Netherthorpe. Both are great airfields to visit.
Good luck