Probably you have already had replies, in case not - this is usually played
as a transposing instrument when playing the traditional NSP tunes. i.e.
you read G but it sounds D (the note above middle C on piano).
It is up to you what you do when playing any other music.
In other
1) Yes.
2) That depends. The note you get with only the R little finger up on a D
chanter is D. Most folks who play Northumbrian tunes on D sets play them with
the same fingering as on other pitches of sets, so a tune that would come out
in F on a traditional set or G on a G set, comes out in D