The 146 is pretty robust, so you just need to check a few things -
Does the engine run smoothly, with no smoke...?
The T/Sparks can use oil "as normal"... but not silly amounts. Aave a look at the oil level - it should be clean and on "MAX"
Does the gearbox change smoothly...?
146 does not have any gearbox issues, so this should just work
Is the clutch light...?
Clutch can last over 150,000km so if it's not recent, it might need changing soon
Is the suspension silent...?
The 145/6 front suspension geometry gives the suspension wishbone arms a hard time, so the bushes can wear out. Check that the car tracks straight and look for wearing out on the inside of the front tyres.
This should be quiet. No specific problems.
Check the rear brake discs. If they look "rusty" or have a band round the outside that is not clean, then the rear calipers probably need refurbishment. They don't get used much, so they can seize up slightly. The discs should be shiny/clean over the whole of the working surface.
Also... find out when the cam-belt and tensioner were last changed. They need to be changed every 3 years/60,000kms. The seller might be selling because this job is due.
Ask if the variator and water pump were changed recently (they can be done with the cam-belt change.. )
It's good practice to change the water pump every .. or every second cam-belt (so 120,000kms minimum)
If the engine sounds like a diesel when you start it, it needs a new variator.
Check the floor to make sure there's no corrosion in the footwells. 145/6 can rust at the rear of each footwell.
The dashboard and bumpers etc all swap over with no problems... but don't worry about that yet. Make sure the car is mechanically A1. When you've got it "sorted" then you can add cosmetic changes..
Good luck with it..