Hey welcome to the gang!
Most likely, if the was made in 76, then it is a k6, but it depends on the vin. AS a rule a thumb though, if it was made before, say, november of 76, it is a k6. If you look on your vin plate, it will say for sure. My 78K was actually made in december of 77 but is badged as a k8.
As for issues, there are not too many really. The gears do not like to stay engaged when under a lot of power. Not really an issue unless you mod the engine to produce a lot of power. The electrical system is not very power. You can switch to a h4 halogen 55/60 watt bulb but if you start adding other lights, you might run into trouble, especially since charging is minimal under 2000 rpm.
If you go through the wiring and clean all the connections and either replace with better connectors or solder them, that will help a little. An electronic vreg with help also.
Most issues are simply maintenance issues but keep in mind, this is not a 10 year old bike, it is 35.
After a period of time, things will need work no matter what. So if you do not know much about the work history, keep logs and keep an eye on things. you may be replacing head gaskets at any time or something else like that. So, inspect the bike fully. If you have questions, don't hesitate to search here and ask. If you can, include pics as it is usually easier to give a better answer.
On to your cafe. Google cafe and you will get a good idea. the 69-76 bikes lent themselves very well to this look. A set of clubmans, a new seat, and some rearsets and you are on the way. You don't need rearsets but they help the look, otherwise your legs are more cramped.
Much of the rest is cosmetic changes according to your vision.
The ride IS the adventure. The destination is just to get gas!