This is the information I have on my TomTom:

[ID]
LocalID = ['one2008_t_2048_m_tts', 'one2008_t_1024_m_tts', 'one2008_t_2048_m', 'one2008_t_1024_m', 'one2008_t_512_m']-8.083.9669.small-8.083.one2008_t.CAB-navcore-ONE
imageID = None-None.None

[Image information]
Birthday = Monday 17 August 2009, 17:58:48
Image type = CAB
Item number = 8.083.one2008_t
Item description = CAB-navcore-ONE
Changelist = 344415
Application version = 8.083
Application build = 9669.small
Linux kernel = 343369
Bootloader version = 55136

I want to update my map to the current US only version. But, I don't know if my navcore is compatible.

As I understand things:
step 1 - get latest navcore from ttHome
s2 - find and download map *stalled here!*
s3 - copy to device
s4 - patch device, map, and ttHome
s5 - enjoy!

Am I missing anything? I haven't done this before.

Go to the All new 875 maps thread and check the chart - it shows wich map version is compatible with a specific Navcore version.
Download the map version of your choise that covers your area.
Follow the instructions provided in the first posting.