Hi komet, No special tools are required but a set of whitworth spanners . Take time and patience when dealing with rusted or siezed parts,a good gas blowtorch to apply heat to stuck components and a decent releasing agent to soak parts will help too.
At the end of the day it is a Lister diesel engine built to be abused for years workwise and is built like a tank.
The manual will be a great help.
Hope this helps