Just wanted to update this thread with my experience in filing 5500-EZ for my self-employed 401K plan for the first time, since my balance exceeded $250K (threshold for requiring filing).
I printed out the paper form, read the instructions, talked to Fidelity, and did some browsing on the internet. The Fidelity agent pointed me toward their website (search on form 5500) which has a useful image of the form and line by line explanations plus some guidance on which plan characteristics apply.
I did register for an account on the EFast2 system (set up by Department of Labor) and filed my 5500-EZ electronically. I liked that as I entered my data on an online 5500-EZ there was some error checking. Also a field that I erroneously left blank on my paper draft (6c net plan assets) was automatically filled in by the program. There was also a validation check before submitting the form. Finally, after filing, I received a confirmation number, then shortly after a status showing "filing received". The only suggestion I would make is generate a PDF copy of your return for your records before filing as once you've submitted it electronically, there doesn't appear to be a way to retrieve a copy on the Efast2 system.
