Any MP20 upgrade to an MP40W is just a different driver and power supply, wet end & dry side remains the same.
LED issue is whether you want to upgrade to the newest MP40WES driver or not.
Did a swap on one of my Vortechs, very simple. Simply pry open the driver box, unplug a connector replug that connector in the new driver and snap the cover back on the new driver. Very important, you must use the power supply included w/ the upgrade kit. The difference in power is very noticable, so I loved the upgrade.
Good luck.
the es are the newer ones. a few minor changes in some of the programming options but I'm not sure its worth the $100 per driver or whatever they are charging.
anyway, i have some old mp40w driver boxes if you want to try the upgrade. give me a couple frags and they are yours.
EDIT: just looked at the dates, and this was a two year old thread. hope you managed to upgrade by now