You should be able to download both manuals at
www.competitionx.com
The cars are essentially the same - minor differences to materials and drivetrain chouice, but parts are interchangeable.
You could lock the centre diff using Egress/Vajra parts or run the centre one way bearing. The 'new' Egress gears are the same as they were 20 years ago
The old slipper plates were notoriously badly pressed and far from flat - even when new it was best to wet sand them flat with fine wet n dry paper. You should be able to buy a new differential bag (plates and balls)from ebay or somewhere like
www.vintage-tamiyaparts.com