My 2003 Nissan Altima automatic transmission has a hard shift from from 1st gear to second. It makes a bad noise like when a poorly transitioned change of gear in a manual from one to two. It gives the error code P0745.The rest of the shifts are perfect for now. Something to do with Line Pressure Solenoid Valve. I read I could replace the dropping resister or check it. Where is it located? What else can I try on my own? I am quite handy. Please give me some steps to follow and the location of parts and locations to check.

Don't know about The Altima, but the resistor is usually located on the driver strut tower.
The resistor looks like a rectangular metal sometimes rusty with 2 10mm bolts and a 2 wire plug