- Do dogs, or GSDs, groom themselves and to what extent?
Most dogs do not really groom themselves. They may lick their paws and their private parts, but otherwise, they aren't really able to groom themselves the way a cat would.
- I groom her twice a week with a undercoat rake and dong groom for guard hairs, but how would I treat when she is all muddy on her paws and belly - do I spray with a water bottle?
You could, or you could just use a damp cloth or towel, or you could simply hose the legs and belly off if it isn't too cold.
- How would I clean her ears?
Use a commerically prepared ear cleaner for pets, or you can mix up a solution of white vinegar and rubbing alcohol. Squirt a bit into each ear, rub the base of the ear, then wipe out the dirt and wax with a cloth or cotton ball. GSDs don't usually have ear problems, but it's really good to get them accustomed to having their ears cleaned, as some dogs don't like it.
- How would I now when her toe nails are (too) long?
If you can hear them ticking on the floor, they are probably long enough to trim. Use a pliers-type nail trimmer, the Resco guillotine-type are awful. Trim off just the sharp tip of the nail, a little at a time, until you see a dark spot in the center of the toenail. If you go any further they can bleed, so less is more until you get used to doing it.