Short answer: No.
The difference you see in the sheet music is that for guitar you use the G clef and pianos use both the G and F clefs. This is not much of a difference except for the visual part. The notes are notes all the same. You can learn to read piano music in 5 minutes to know the F clef plus a week to get used to it.
About composing, if you don't have the time to learn what pianist-composers learn, you don't have the time to learn composition at all. Like Matthew said, apart from the technicalities of each instrument, the music itself is all the same.
A hint for a guitar player is that if you start in one area as opposed to another you might get some results quicker. For example, 'functional harmony' (I learned the term in Portuguese, I'm not sure they call it the same in English), the one that deals in terms of dominant, subdominant, etc, might be more quickly useful than say, the kind of harmony in Schönberg's "Theory of Harmony".
Learning that after a G7 chord you can have a C chord might be more useful than learning conduction of many voices in the short term. But if you're serious about composing you'll have to go through it all eventually. Harmony, counterpoint, structure, the whole thing.