Insurance
You will probably want to insure your puppy and I would strongly recommend that you do. The Kennel Club does run a scheme for breeders which enables them to issue a cover note for the Kennel Club pet insurance for six weeks. I do not do this because once you are enrolled on this insurance you then have to opt out of it when the six weeks are up. I think it is much better that people find an insurance policy which suits their needs (and budget) rather than have one foisted upon them which may be unsuitable and/or excessive for their needs.
You can easily compare the offerings of different pet insurers on price comparison web sites. It is worth taking a little time to do this because premiums vary quite a lot (just as it pays to shop around for your car insurance). For what it is worth, insuring each of my adult dogs costs me about £90 a year (which is not with the Kennel Club).
The reason I think you should insure your puppy is not to cover vet's bills or to pay the cost of a reward if the puppy goes missing. I have never had to use insurance to cover vet's bills because I have never needed to use a vet for anything other than checking the health of puppies before sale, annual vaccinations, pet passports and stuff to do with mating dogs which needs blood tests to pinpoint the exact day, scans etc. Also, German Shepherds just do not get lost. They stick to you like glue.
No, what you need insurance for is something which most people do not think about and which is something you hope will never happen. This is third party liability insurance. This comes with almost every insurance policy as part of the package but, so far as I know, you cannot buy it separately. Third party liability insurance is very important. It isn't about your dog biting someone (although third party liability insurance covers that). It is about the possibility of your dog causing a traffic accident.
Say, for instance, you momentarily lose control of your dog as he runs after a cat, a squirrel, a pigeon or whatever. Even with the best trained dogs this type of thing can occasionally happen. And say that your dog runs across a road causing a car to swerve and crash. If a person is injured in an accident like that then the car owner's insurance company will sue you. Damages for personal injury can runs into tens and sometimes hundreds of thousands of pounds. Even if you were only partially at fault (because, for instance, the car was speeding) then even a proportion of such damages will make it a very, very expensive accident. It is something you hope will never happen and the risk may be small but if it happens the financial consequences could be catastrophic for most people. This is the main reason why I think you should insure your dog.
But shop around. There isn't any point in paying for more cover than you need or want. And basic cover for this sort of third party liability is relatively cheap. It just isn't worth running the risk of being without it.