the fender must be well loosened or removed to get to the hinge bolts
Most rust can be removed by a steel brush if its not to rusted
The engine has to be removed.
there is a clip on the back side under the fender. usually rusted so a new one will be needed when you change marker light.
The best product to remove rust is limeaway. That stuff will remove anything staining including rust. It will not damage the actual item that was rusted. Only the rust will be removed.
Hit it with a hammer
Hacksaw
Bad news. I have found it impossible to remove the bolt caps without breaking them. They are mortared on. They do make plastic bolt caps in a lot of different colors.
A cutting torch is one answer.
Put in Hot water
I did it in about an hour and a half, but I had no problems like rusted bolts etc to slow me down.
A magnet
a large hammer