I just replaced my engine wiring harness after my car has been sitting for 2 months. I tried starting it and it kept rolling over, but never starting. After about 3 seconds the battery voltage would gradually die down. Should I replace the spark plugs or what?

 

nope. its probobly just flooded. do a search for unflooding procedures, should turn up what you need to get it started.

 

pull the plugs first and see if they're wet (flooded)

 

I got the car to start! However, now it seems like something is locked up. I'll hit the gas, but it seems like im in a pile of mud trying to drive up out of it.
Are the brakes locked up, and if so how do i fix it?

Thanks

 

did the e-brake stick on? your rotors might be rusted up a bit, nothing a little drive with some braking won't fix...