How easy is it to change a thermostat in a peugeot 406 HDi diesel 1.9l?

RE Peugeot 406 turbo diesel 1.9L HDi 110 bhp

The engine takes forever to heat up. I want to see if it's the thermostat but I'm not exactly sure where the thermostat is housed. Is it a job that a reasonably technical bloke could have a go at?
Where is it mounted? There seem to be 2 hoses coming from the radiator.
dave