It sounds like multiple problems occurred. I've heard of the first one, the one involving VSTO 3.0 SP1. I think it arises when there is a network glitch while the NodeXL installer tries to download VSTO from the Microsoft site. The solution
is the one you used.
However, I don't know why the installer was trying to install VSTO in the first place, because if there was a previous version of NodeXL installed then VSTO would have already been installed. That's a mystery.
If the problem involving Dnrd.msi happens to you again, please send me the error message if you can. I might be able to figure out the exact cause.
When I've messed up NodeXL on one of my development machines (usually while dealing with multiple versions), I've found that the Repair option, rather than the Uninstall option, fixes it. That's another thing to try if this happens to you again, which
I hope it doesn't.
Thanks for letting us know about your unhappy experience, and for having the patience to work through it.