I have not used the 1.4 so I can't really compare them. But my guess is that for the sorts of things you are shooting the 1.8 will be perfectly adequate. If you were a pro trying to sell pictures, etc then maybe you would notice enough difference to justify the price. But for an amateur whose photos aren't critical I think the 1.8s would be fine.
Once you learn Capture NX2 it is not that hard. And the things it can do are frankly amazing without much effort. There are some good books out there to learn the software and some very good video tutorials on YouTube.