Incremental Upgrade?



I recently purchased a new (to me) boat and "think" I have a 10.5 model 1824C marine radar unit with a GD-1920c C Map plotter. Serial is 4323-5117 and software is 195002404.01.07*.

From reading here I probably need to update the software and need to do it incrementally.

Can you confirm this and provide links to the various upgrades so that I can proceed.

Not sure I'm looking in the right places.

I tried the 4.03 yesterday and the unit just beeped twice and started normally.
Do I need to go to the 4.02 first?
If so, can you please provide that link.
If not, what am I doing wrong? I unzipped to the root of a 2GB SD card.
I just went through the whole thing again and this time IT WORKED!
Much improved, thank you.