It's easy, if you know what you are doing it should take you about 15 min including replacement of PCV valve grommet.
On 4 cylinder it takes about 20-30 minutes. For V-6 it might take couple hours.
It's not hard but time consuming.
The oil leak is coming from the valve cover gasket and leaking onto the exhaust manifold, the rubber valve cover gaskets get hard from the engine heat and start to leak, you will have to replace the rubber valve cover gaskets to stop the oil leak
Check the Camry air filter for a clog. Check the ignition for a weak output, and the fuel filter for a clog.
Switching valve for EGR (4 cylinder model) is located on the side of the engine facing the firewall it's next to the knock sensor. It's hard to access, if you want to replace you need to jack up your car and do that from underneath the car.
How hard would it be to replace oil pan on 1996 Sonoma?
On Camry 99 it took me 20 mins to replace the right side. The drivers side take about the same time.
how to replace water pump on Nissan quest 3.0 1995
Sometimes a piece of carbon will get caught in the EGR Valve. If is is hard starting, idles rough, and the brakes are hard, check the EGR Valve, it probably has a piece of carbon stuck, keeping it open.
Do you have heat when you turn the fan on?
It's not hard, it's very easy.
Its old, google how to clean (ICV) idle control valve.