Is it hard to replace engine seals?

It's Hard. Replacing a rear main seal is time consuming, requires special knowledge of your vehicle and the use of special tools if you are going to do it correctly and without placing you or your vehicle in danger.

If your inspection shows that the leak is coming from worn rubber seals or gaskets and isn't severe, using a stop leak additive or high-mileage oil blend can be an easy solution. These products are designed to soften and condition rubber seals, which helps prevent and stop minor leaks.

How to tell where oil is leaking from?

Oil that is older will likely look dark brown or black, says Angie's List — adding that you'll typically notice oil leaks directly under where the engine was. Oil leaks often come from gaskets or seals in the engine, valve covers or the oil pan, according to Cars.com.