With the 8011, you get a lot of tractor for your money.
The problems that you list are minor. A can of WD-40 and some elbow grease will sort out the foor throttle linkage, the PTO lever and the torque control (hare/tortioise).
A water pump costs in the order of 80 (50). Not difficult to replace either. If your one isn't leaking, I'd leave it for now.
Rear tyres - new rears 16.9 R34 cost about 300 (200). I hear good reports about Barum - the forestry folks like them so they are TOUGH! Front tyres cost around 80 (50).
Brakes cylinders are a problem but search the site for suggested replacements. What I did on mine was to fit mechanical brakes i.e. rods to operate the brakes and forget the cylinders all together. This works for me.
What
oil pressure reading are you getting?
Is the hour meter working? 5000 hours is not a lot - then again this is more likely 15,000 hours or even possibly 25,000 if it had been well maintained!
Do you know anything of the tractors previous history? When this tractor was bought 30 years ago, it wasn't to mow lawns.
What will you use the tractor for?
The good
news is that is wont cost and arm and a leg for the parts you mention. The things you list are very repairable.
Tom