How to upgrade from 5.2.1 to 5.3 with only remote access

[Chris Hastie]

Hi

I'm sure there must be documentation on this, but I just can't find it. 
Plenty of stuff on upgrading from 4.x to 5.3, but nothing on upgrading 
from 5.2.1

The situation is that I have a remote, leased server running 5.2.1. I 
have ssh access only, no console access or terminal server, so anything 
involving single user mode is not an option. I believe the original 
installation was a binary installation, though I have since installed 
some of the source (using sysinstall) so that I could customise the 
kernel.

What is the most sensible way to set about performing this upgrade? Is 
it even possible?

Thanks
-- 
Chris Hastie