Sounds like it's a "2D" lamp, like two capital D's back to back. If it is it's a straight pull from about the centre of the lamp, there is a fair resistance, then the whole assembly comes away. You'll see either two or four brass coloured pins, make sure you buy the correct replacement.
DIY stores are a bit pricy for these lamps, try a local electrical trade counter first.
You should be fine just switching off but safety first, you're in a new build so use the mini circuit breaker that protects the lighting circuit.
The flickering may be the lamp at the end of it's life or a dodgy starter. If there's any blackening where the two D's meet them most likely the lamp.
Hope this helps.