Quite difficult but not impossible. But you need a wire loom and a switch to the front, and a lot of other things. Might be cheaper and less throublesome if you install a new or used second hand one.
The gear however makes a lot of trouble. Get's worn. Sometimes on Ebay offer replacements made of steel (DIY ones), which cost abt. 40 $. Original gear is made of plastic and not available as single item.
On my page there is a link to Evansweb where such a repair is described. I would stick to the manual one. Actually I use it very seldom.