I think that your manual suggests a fluid change at 100k miles, so while it would have been nice to change it earlier, you have not been negligent.
If your fluid is badly discolored at 70k miles, I fear that you have a problem, so it may not much matter whether you drain or flush. Do one or the other and cross your fingers.
Remember that draining the fluid gets only about half of the fluid out, so you will be mixing fresh fluid about 50/50 with old brown fluid. For that reason, I would tend to want to flush it. However, this is not the first time I have heard that Honda does not recommend flushing their transmissions, so I guess it is best to believe them. It should be pretty easy to drain and replace your fluid. There is even a video doing it on a CRV on uTube. However, if your fluid is discolored, you may want to clean the screen and the pan, and that will be a lot messier. Honda also insists that you use their fluid, but a Google search should identify the manufacturer of their transmission fluid so you can probably get it cheaper elsewhere.
Some folks say that putting fresh fluid in an old transmission causes it to fail. That is like observing someone die after taking aspirin to ease the pain from a brain tumor and concluding that the aspirin killed them.