Just bought my first diesel. Found a great deal on an '02 with 41,000 miles. Runs great and looks like new. A friend checked and found out I have low fuel pressure,(6-7). I bought a FASS DDRP to replace the lift pump. Discovered the truck has a retro-fit in tank pump. Can this be removed and the FASS be mounted on the rail? Service rep at the Dodge dealer says the in tank setup can't be removed because it's now tied into the PCM. I located an original fuel level sending unit module to to put back in, in place of the in tank unit. What headaches am I going to encounter in this swap?