It is not tricky to assemble the parts (because the trick with the I2C is that you can just connect all SDA (Serial DAta) pins together and all SCL (Serial CLock) pins together and it usually works). Just make sure that you have the python libraries in the right directory and the I2C is enabled on your Raspberry Pi (the I2C Master).
Of course you need a power supply as well. Display is supplied with 5V (VBUS). BMP280 is supplied with 3,3V (VCC), Pins SDO and CSB of the sensor are connected with VCC (here a soldered connection).
BMP280 tends to overshot (temperature) if it's exposed to direct sun radiation, so I would recommend to mount it at a rather shadowy place. The atmospheric pressure measurement is very delicate and accurate, as far as I can tell.
You can run an MQTT script simultaneously without any problems on the RasPi (for remote control).