Couple of problems with my truck

So I bought this truck off my uncle for a great deal and it has 199k miles on it.
Truck is fully loaded all the options.
1. My light to my PRND and mileage keep going in and out and it's driving me
crazy. I know its a connection issue but is this easy and where would it be
located.com?
2. Oil pressure is at like a solid 60 when I am driving the car, but when im
slowing down or idle, it flickers between 40 and 60. Is this an issue or will it be
fine?
3. It has remote start and i can get the vehicle to start but 2 seconds later it
turns off. Where do I start to look for the problem?

Thank you in advance for the help.