<if i just slightly cook some sausages, and then chuck them into my slow cooker with potatoe, carrot and onion with some beef stock will it all work out?>
It will cook, and you'll be able to eat it. The sausages might make it a little fatty, however. Best to use a low-fat meat for slow-cooking. But it will work. Why not add a little chopped celery, a capsicum (red or green), maybe some corn niblets, some beans or peas; maybe some finely diced bacon or ham; a finely chopped chilli for oomph if you like oomph; and a pinch of herbs to add extra flavour? Chives, thyme, parsley, some pepper, rosemary, sage or a bay leaf, maybe. How about a dash of Worcestershire sauce or soy sauce?
Herbs turn a meal that could well be ho-hum into WOW!
BTW, nobody is a hopeless cook. In my language, 'hopeless' in this context means either 'inexperienced' or 'downright lazy'. I think you just need a basic recipe book and some practice.