This topic has been covered quite a bit in this forum. If you do a search for "Blood pressure" and "Hypertension" you will come up with some good threads such as
This one.
You can get your BP checked easily at your GP's or at home using a bought monitor. A lot of the monitors are good enough to be useful, and makes such as Omron have a good reputation. It is important to get the right cuff size, and it is usually better to stick to cuff style monitors.
BP readings in isolation are only a spot indicator of something that varies throughout the day ordinarily. If the reading is indicitive of hypertension (high blood pressure), it will be retaken after an addition rest period. If it is persistently high then you may be referred for further monitoring.
As you say your lifestyle has a number of high risk factors and it would be sensible to address them sooner rather than later. If you intend to stop smoking, now rather than after the medical might be a good idea. The impetus is less likely to be there after the medical ?