A Durga is suitable for brushless, but a slipper clutch is essential (I melted my rear diff first time out with my brushless system without a slipper), and there are a few more upgrades that are advised too.
See this thread for more advice
If you buy a second hand brushless system from someone reputable on here, you should be fine (I'd avoid ebay tbh). But you really need to upgrade to lipo too, as the power needed for brushless is more than a nimh stick pack can generally deliver.
If you shop around and get lucky, you should just about be able to do what you need for the money.