Aside from a 50% speed boost the Morgan has the same "guts" as it were as the Athalon MP (minus the extra cache of course). That means that if you want to have the full benefits of the chip that you'll have to do a complete reinstall of your OS. If you just switch chips the system should run stably but it won't have access to all the updated features.
Post your system information, motherboard, RAM (speed and manufacturer), HSF etc. You may get a better return on the money spent by upgrading to one of the later motherboards with the KT266A chipset. Several of the better performing motherboards can be had for $75 or less.