I've heard (from the horse's mouth) that the airframe is definitely not an issue, all the airframes have been totally overhauled and there is little metal left that actually came from the old sprites. They have been zero lifed for a guaranteed 10000 hour lifespan.
That said, the few guys from 816 I have spoken to aren't particularly keen on the Seasprite, despite its capability. More Seahawks would have actually been cheaper by avoiding the cost of integrating a totally new helicopter into the works.
The reasoning behind the Seasprite was that the Navy was looking for a small ASuW helo they could fit onto their new fast attack ships they never got (+ more to go onto the ANZACs). When that idea fell through the Navy was already comitted to finishing off their investment with the Seasprite.
However, having looked over the airframe recently it is very hard to not come away with a sh*t-eating grin plastered on your face. The cockpit is something else, four colour LCDs combining all the systems onboard - and there are a sh*tload of them! The only analogue instrument I could find was the standby AI and that was it.
Cheers