what you need from the seller is a notarized DOS, original copy of the OR and CR, release of chattle mortgage (including bank certification) if applicable, photocopy of 2 valid id's with specimen signature. it would be much better kung may TMG clearance na sana before kayo magbayaran.

depende sa maintenance history pero kung doubtful ka, you can never go wrong with changing all fluids ( engine/ATF/differential/rad coolant etc). check mo din timing belt vs mileage, again if duda, palit na lang para peace of mind.