Gary,Trying to get music notated without knowing how to read or write it is somewhat like trying to write a novel without being able to read or write English (or whatever language you speak). You could get a software program that translates your speech into the written word, but you would have no way to edit it or even check to see if it accurately wrote what you said. The same is true with notational programs. Finale will import a standard MIDI file, but the notation may not be close to what a live musician would expect to see.
I suggest that you learn to read and write music. If you are composing symphonies in your head and on a sequencer, it would not be too difficult for you to learn the fundamentals of musical notation. I work with a lot of people in situations similar to yours and they have produced some music that sounds great on the sequencer, but is not playable by live musicians. The problem is that a sequencer will play notes that are not even in the range of some instruments and/or passages that are too technically demanding for all but the best musicians to play. You also need to be aware of the notational conventions that musicians are used to seeing, i.e., dynamic markings, tempo indications, bowings, etc. Most of the people I have worked with have picked up on music reading quite rapidly and have had no problems getting their music properly notated. I am sure you can do so, also.
Although some programs claim to be able to produce standard notation from MIDI files, they generally will not get the job done alone. They still require the guiding hand and mind of someone who understands standard notational techniques.
All of the good notation programs, like Finale, assume that you have some concept of notational practices and are somewhat difficult to learn at first. However, with Finale, you will have total control of the look of the final product. Most of the others will generally produce 2nd or 3rd rate printouts that you are unable to alter and that the symphony members and conductors would not want to deal with.
You may want to consider starting with Coda's PrintMusic! or Finale Allegro until you feel comfortable with computerized music notation. If you want to move up to Finale from either of these programs, Coda provides a reduced rate upgrade package from both products to Finale.
You also might want to try Practica Musica from Ars Nova as a way to learn how to read and write music as well as improving your listening skills. It comes with a text that is well suited for musicians with a limited knowledge of theory.
By the way, I do not work for either of these companies, but I do believe that their products are among the best in the business. I use both Finale and Practica Musica in my freshman music theory course at the university and have found them to be quite helpful to the students.
Sorry for the rambling, but I hope it gives you some ideas about how to proceed.
Good luck!
Jim Coull