Starts sputtering and running rough after fifteen minutes, does not go over 55 mph

After it starts to do this it only sputters and lurch and drive rough when accelerating, after I get to speed and hold it there it drives pretty normal besides here and there it will sputter hard. When I slow down to stop of it is driving especially bad it will shut off but sometimes when I stop it will just sit and idle fine until after a bit it may sputter out. The harder I hit had pedal the worse it drives and It seems like sometimes it runs really rough and car shuts off and when driving it have to keep foot on gas to keep it from shutting off but others it runs a little rough but doesn't shut off.
It is throwing these codes:

P0300 multiple cylinder misfire detected
P0301 cylinder one misfire detected
P0315 crankshaft position system variation
P0335 Crankshaft Position Sensor "A" Circuit Malfunction
0442 invalid data received from TCM

I was thinking it was just c crankshaft position sensor but I'm not so sure, We have been driving it like this for probably going on six months because things got bad and we had no choice and no clue what it was. It hasn't gotten any worse.

If I change the crank position sensor myself is there anything special I have to do? Someone told me I have to put something in the right position for timing or it will run badly or not at all. I have changed one before in another car and never did anything extra?