I've been cleaning my own sensors myself for years. Sure it's intimidating at first, but it becomes so second nature that I do it as a matter of course now whenever needed.
The smaller the aperture you use, the more visible the dirt is on the sensor. An image shot at F5.6 might not show specs on the image, but may very well show the specs clearly when shooting the same inage at F12.
Here's what I used to do:
Remove the lens and set the camera to lock the mirror up for cleaning (you'll find that feature in one of the menus). Once you selected the feature, press the shutter button. This will flip the mirror up to expose the sensor behind it. The only way to get the mirror down again is to turn the camera off.
1) Next step is to use the rocket blower. Make sure you point the lens opening of the camera body down and blow up from underneath. That way any dirt that is dislodged drops down away from the camera. If that does not get rid of the dirt, then
2) Use the Arctic Butterfly brush. This is a motorized brush that vibrates the bristles to build up a static charge. Turn the brush on and charge the bristles. Then turn the brush off and gently sweep across the sensor from one side to the other. Sometimes this gets rid of any dirt not removed by the rocket blower. The dirt is attracted to the statically charged bristles and sticks to that.
3) If the brush does not get the sensor clean, then I use a gel stick on the sensor. Gently pressing the sticky gel pad on the sensor repeatedly tends to pull all the dirt off the sensor and it then sticks to the gel pad.
4) In the unlikely event that there is still dirt left on the sensor after using the gel stick, I use a wet wipe to clean the sensor.
5) Once you've finished cleaning the sensor, turn the camera off, re-attach the lens, select a small aperture like F18, turn AF off, point the camera at a clean sky, either blue open sky or a section that's evenly clouded over. Take a picture and evaluate in your photo editor to see if there is any dirt remaining. This specific step is one I do between each of the cleaning steps. Obviously, after any step if the sensor is clean there's no need to move to the next cleaning step. The reason I turn AF off here is because the camera won't focus on clean sky with no contrast. and depending on the mode selected the shutter may not fire if the camera cannot lock focus. Also, focus or the lack thereof does not make a difference to how the dirt on the sensor displays in the image.
Over a period of a year or so I purchased the rocket blower first, then the Arctic Butterfly brush, and then the wet cleaning wipes. The gel stick only became available relatively recently. SInce I purchased the gel stick over a year ago I have not used the brush or the wet wipes. I now start with the blower and if that does not remove the dirt, I move on to the gel stick, This has worked well for me with both my D7500 and my Z6 bodies.