My 40k miles 2006 2.5 WRX Hawkeye's gearbox is beginning to whine, it's worse in 2nd and 3rd, and occasionaly it's difficult to get into 5th gear.

I've had the car a few months, and the gearbox was perfect when I took delivery of the car. The gearbox oil was changed at 30k and I changed it at approx 38k.

Hands up I've really used the car hard lately, I've been doing a cross country B road commute at 3am, 6 days a week should I be expecting to rebuild or replace the gearbox? Can the original 5 speed gearbox be rebuilt to a stronger spec?

The car is standard power, but having a remap Friday. In the future I'd like to take the car past 300bhp.

Suggestions please?