If you've got a VR lens, then you're good to go, and if you don't find yourself wanting a wider angle or wanting to reach out some distance, you really don't need wide angle or telephoto zoom. The on camera flash (the one that pops up on top of the camera) is useless more than about 10 feet away, if it's totally dark. However, even in the daytime, the flash can be a useful thing...for example: You are taking a photo of someone/some object that is a few feet away against a brightly lighted background...in other words, pehaps the sun is behind your subject...then pop the flash up and use it as a fill light to light your subject, while still properly exposing for the background light as well. It takes a little reading and playing around to set the flash to the right power output, but it can really make a difference in the photo. We've all seen photos of a person standing against a sunlit background, and the person is barely distinquishable because the camera is fooled by the background and underexposes the subject (the person)...on the other hand, if you expose for the person, the background will be "blown out", meaning it will look too bright. Using Flash in those situations, but using it in such a way so that you really can't tell flash was used, makes for a much better overall photograph. The whole key with flash is to be able to do it well enough that people can't tell you used it when veiwing the photo. It's worth learning a little bit about all that, IMO...today's cameras are really "smart"...the trick is to know when the camera might be fooled because of unusual lighting, but 90% of the time, the camera is probably smarter than you are.
If you're talking about the LCD on the back of the camera having a spot in the lower right corner, that's probably not the sensor being dirty, but could be a flaw with the display itself. If you download the photo and it looks fine after downloading, then the LCD is just a minor bother.
What you have seems to be working well for you, so why change anything unless you want to get a lot more "serious" about photography in general...then the higher end camera bodies and lenses come into play, but be wary, you can sink a LOT of money in camera gear before you blink your eyes good. I've spent tens of thousands of dollars on gear over the years, but currently have "fine tuned" my gear to suit 95% of my needs.