Your going to have fun, flats fishing is my all time favourite.
You may find it a bit harder if the rod speed you are given is much faster than the one you are used to but with a bit of practice you will figure it out but a 8wt will wear out your arm faster than a 6wt.
The toughest thing for me to deal with was casting in the wind, the flats are rarely dead calm so now I spend all my practice time casting on windy days.
Like Hook mentioned accuracy is more important than distance, your guide will generally get you within 40-60 before letting you cast, Bones are incredibly weary so if your cast isnt where it needs to be, forget it. Once spooked you will be looking for new fish and some days their aren't a lot of opportunities.
I recommend practice casting on a windy day and move around so the wind is coming at you from different directions.
If you can hit a trash can lid at 70' in the wind regularly you will have great success.