Bumblebear, a good idea is to tell the butcher for how many people the roasting joints need to be, e.g. shoulder in joints for 4 people, 1 large leg to feed 15 people at Christmas... rather than trying to guess the weight of what you'd like. The butcher will then automatically know the size required.
Sausage meat is simply mince that sticks together more than normal mince, and you can do this yourself. When you have mince and make, for example, a kind of spaghetti bolognese sauce (very nice with pork instead of beef
), the mince will fall apart into bits in the pan. But if you make meatballs or burgers, you kind of squash the meat together and pat it a bit into shape, and it will hold its shape in the pan. Sausage meat is like mince that's been squashed / kneaded / whatever you want to call it, but for longer so that the texture changes to a mince that sticks together very well.
I just use the egg beaters of the electric handheld mixer when we make small batches of sausages, as working the meat by hand gives me freezing cold hands (since it's kept at fridge temperature) and I hate the cold
Having said that, we don't make many sausages anymore, it's easier to make meatballs as it's quicker and easier to try new recipes.
Re livers etc, ask for what is called 'the pluck'. The pluck consists of liver, heart, lungs, and some connective tissue and bits e.g. oesophagus or windpipe bits. Yucky the first time you see it, but you get used to it very quickly and it's all part of having livestock.
When you take the pluck out of the bag, you'll be taking it out as one pack of organs and cut off the liver, heart and lungs (if wanted), and discard the rest.
Kidneys are not part of the pluck, they are cut out of the carcass separately, so just add them to your list.
Also get the head for headcheese. You could ask to have the jowl removed for curing (gunciale). We found the head difficult to deal with the first year (the gross factor - I couldn't face looking at them the first year) , but you get used to all these cuts.
The trotters will make excellent jelly.