Lost in upgrading radio

[explorer2k]

Hi all,

I've spent the lat 5 hours reading here, bricking my phone into bootloader stuck, and back with no luck.

I'm running Nuerom 5060 and want to upgrade.
Except from what I read, I can't do it with Radio 3.35 (phone shows 3.35.04).
So, I'm trying to get to 339.
I have downloaded radio339.zip, and tried to upgrade.
Each time I do, it goes to 8% and fails.

I'm using a 6800 on sprint.

What am I missing?
How do I do this?
And am I right in NEEDING the new radio?

Thanks in advance for your help and holding back the "search" comments.