The brake linkages and rock shaft need to be freed up and lubed as GL indicated.
I made a brake pad from an unused automotive disc brake pad. Cut the pad material off with a band saw and shaped with a belt sander. Glued the inside pad in place with epoxy.
The needle bearing part no. is MTD 741-0154 and is available by search.
Part no. for the fan is MTD 931-0317. Several sources are available. Best price I found was $25 with free shipping.
The return spring is part no. MTD 932-0121. Available by search.
The right pull bar can be made (same as the left) or ordered from On-Point Welding. He makes hitch parts for the 990. Scroll down to see the pictures of the hitch and parts.