Congrats on the purchase - sounds like it was a deal too good to pass up. Did the owner make any mention of the clutch? Seems to engage pretty smoothly?
Redline MT-90 75W90 is a synthetic GL4 fluid and one of my personal favorites. Good mix of noise reduction and smooth shifting, even at colder temperatures. Pretty popular choice for oil. Castrol SYNTEC, AMSOIL Severe Gear, Motul, Valvoline SynPower, are Royal Purple - are others that seem to be popular with many as well. As long as you drain and replace the fluid at regular intervals - should not have any issues with any of those.
With the age and mileage of the car - check the usual suspects. Look for signs of damage and corrosion, and address them before they get worse or cause you headaches down the road. Good idea to replace all the fluids and normal maintenance items, unless you know they were taken care of recently - basically a comprehensive "tune-up":
- drain and refil coolant (Toyota Red, don't forget the overflow tank)
- drain and refill oil and oil filter
- drain and refill transaxle oil
- drain and refill power steering fluid (can be done over a period of time, just siphon out the reservoir - refill and repeat after driving around a bit)
- drain and replace brake/clutch fluid
- bleed the brake lines and the clutch release cylinder and lines
- replace the PCV
- check the condition of the soft rubber hoses and vacuum lines
- replace the sparkplugs
- clean the throttle body
- replace air filter
- replace cabin air filter (behind the glovebox)
- check chassis nuts and bolts
- replace serpentine belt (highly recommend the Goodyear Gatorback Poly-V belt)
- check suspension and steering (rack, tierod, lower ball joint, sway bar)
- check all rubber bushings
- check axle and hub assembly (check for worn wheel bearings, sloppy hubs, worn/torn CV joint/boots)
- check all lamp and bulbs, replace the ones that are visibly dim or dead.