Seat can be easily sorted. just search on here.
Shudder when decelerating or light braking, where from? Could be just a loose engine mount, head bearings might need a little adjustment, warped disc etc. All fairly easy to check one at a time and eliminate and not cost a lot to sort out.
Whats wrong with the clutch, does it just need adjustment?
Most of your problems are relatively small and a lot of people on here have had similar problems and far worse, if you sell the bike as is you will get a lot less for it, sort the clutch and shudder and sell it at a decent price and then go through all it again with another bike that you might find a disappointment as well, that's why people mod their bikes to suit their personal likes/dislikes.