Theoretically instrumentation failures in a glass cockpit aeroplane such as the G1000 should be just as easy to fix - you open the box and swap the offending module - done in 2 minutes. The problem as IO mentioned was finding someone who can do this.
However the mean time betwee failures on the G1000 is over 2000 hrs, whereas on normal instrumentation it is running at about 800 hrs, so likely you will have less downtime due to failures (my turn coordination has just packed up
)..
Composite technology must be pretty good these days if they are even building airliners out of them!