I do all my lead sheets on the computer also.
When I get a request for a lead sheet what I do is make sure they have chord charts and lyrics with them.
I then write the chord progressions for the Chorus and Verses along the top of the sheet.
Then if someone requests a key change, usually to accommodate the singer, just plug in the chords from the new key. Of course it is also a good idea to check that the initial chords for a song work and that you know all, or most of the key signatures. Another reason to understand the Circle of 5ths/4ths.
Really what was supposed to be so special about the NNS software?
Most note values and symbols can be found free on the internet in a font that you just need to install in your word processor font file. The one I use has ♩ ♪ ♫ ♭ ♯ and ♮ For clefs I just copied artwork for them from the internet and resized them accordingly. For staves I just drew them out myself in the word processor program I use.