True to their word, Steinberg has released a FREE 30-day trial package of Dorico that you can download from here.
For any orchestral composer, this program is a must to try. The number of options for virtually musical object can seem daunting at first, but gives you incredible power to express your music in the exact form that you want.
There are some things missing that will frustrate guitar players and composers: there is no tablature, nor chord symbols. I am assured that these will come in time, but they are non-trivial items to add to so complex a program.
You may find that the learning curve is somewhat steep due to the evolving state of the documentation. If you are new to Dorico, watch the short instructional videos that will give you an overview of the program and its five modes. Try working along with them to speed up your learning. You should check out the Dorico Help page when you get stuck. Finally, the Dorico user forum is extremely helpful with several of the Dorico team members very active in answering questions and resolving problems. I suggest that you join right away.
Have fun, and remember that learning any new software takes time, so go easy on yourself.