hmm... give the car a one over by a certified pro mechanic. make sure no major faults, change stuff like air filters, lube oil, gearbox oil, spark plugs etc
just to add on...
timing belt by now shd be due ( or over ) for change as well.
something very simple yet fundamental - by now lots of screws and nuts and what have you can be loose and requires tightening.
a qualified mechanic is required.
Watch out for the engine. Used to drive an ESi. Out of every 10 ESi there is at least 6-7 ESi which have its engine replaced due to overheating. ESi Engine is very prone to this problem. Plus it's an aluminium engine thus once overheated and the aluminium structure within the engine bent, that's it. It will give u hell lots of problems. I used to experience that. Have to top up my coolant water back into the radiator from the reservoir every day cos the engine simply lost the ability to suck back the water from the reservoir when cooled down cos' the pressure within the cooling system is no longer equalized. Also check the Aircon System. Tend to leaks once the car reached this age. Other than that, the rest of the snags should be of normal wear and tear so need not worry too much. Whichever component's time is up just change it. Enjoy the ride. ESi is a very powerful and spacious car. Great to drive if well-maintained.