My mechanic has just changed the engine oil of my 2003 Honda Accord EX 2.4L. I observed that he put in 5 litres of the engine oil instead of 4.258 litres which is the normal capacity of the engine. Please advise me if ths will cause any problem in the car and if yes, please advise me on what to do

If the oil level is too high, the oil can "foam." Instead of the oil pump pumping a solid stream of oil, it will pump oil with air. Obviously, this can be bad, especially for the valves and camshaft which are last on the oil train, experience the highest pressures in the engine, and are usually the first to go. Overfilling, among other things, can also lead to seals being blown out. The best thing to do is to carefully remove the drain plug and drain the excess oil. You need to find a new mechanic.

The FIRST thing you need to do is check the oil level. If there is too much, take it back to the mechanic. If you DO ANYTHING and a problem arises, your mechanic will not take any responsibility for it. Most mechanics will not after someone else has worked on the vehicle.