Yes, you can update it via the SD card if you have a card reader on your PC...however it will take some work as there will be a few things that need to be done.
You'll be able to source another docking station on eBay, there's a few available and they don't cost very much.
Before you do anything, you need to do a full backup of the SD card as it is now by enabling 'Show all hidden files & folders' in Windows Explorer and copying ALL of the contents to a safe place on your PC. When you're confident that you've backed it up successfully, you need to read the following thread and follow the instructions provided:
topic21440.htmlOnce all of the above is complete we can look at updating the navcore and the map.