Fairly simple, as long as you can thread the new cable through the lamp.
If the cable is only twin wire (no earth) then it's just two terminals at the bulb end and two in the plug. The fiddly bit is unscrewing the bulb holder to access the terminals, if there is a floor switch is chewed section before or after.
New cable cheapest is in Wilko -Penge ...? Not a lot to do wrong while your at it change fuse to 3A .