2003 Specialized Hardrock, 2004 LOOK KG386i, 2005 Iron Horse Warrior Expert, 2009 Pedal Force CX1
Based on your description of the 6 notch outer ring, it sounds like you have an adjustable cup and cone bottom bracket. I'd be a little surprised to find an adjustable cup and cone bottom bracket on such a modern bike but I guess it is possible. What does the non-drive side cup look like? Does it have 2 large flats? That would confirm my guess.
If I'm right, you have a square taper crankset and should be able to easily find a Shimano cartridge bottom bracket that will drop in and not require any other changes. Simply measure the spindle and get the same size as a replacement. Will you be doing the installation yourself?
Googling Thun bottom bracket brings up results for 6 notch BB tools like the low end Campy square tapers, which jives with the description of being a cartridge BB.
Makes me wonder whether you crankset uses a ISO taper, however, googling the crankset brings up some other bike specs that seem to use this crankset with Tiagra and Sora components which would be JIS taper.
Either way, you should be able to replace it with a Shimano unit and keep your crankset, but I'm too lazy to chase any further BB specs at this time.
The Thun cartridge should come out with a Park BBT4 tool or equivalent.