Jamesh,
The 540XD is a great club, don't do it.
Take the lessons then hit the driver again...you may find that you can hit it better after some tuition.
The driver swing is slightly different than the
irons you have been hitting with a desending blow (quite correct). The driver is played off the front foot with a sweeping action...also try teeing the ball higher, almost the whole ball above the head at address, the 540xd is a big club.
Hope this helps
Ian.