You won’t miss out on any content by going straight to 5.5 and then updating to 5.5.5. You’ll get it all from the 5.5 update-- check out the size of the NEK 5.5 download.
I just went through this in putting 5.5.5 on my laptop (Mac); had a little trouble getting the second NEK file to download. Maybe you won’t have the same issue with PC.
Good luck!
Chewy