(Don't worry guys, I already did a search)
A close friend of mine gave me her car because she just got herself an 06 GXP and her 99 SE 3.8 with 110k was "not worth fixing."

It needs brakes, struts, alignment and a basic tuneup. The issue that concerns me is a fuel leak and an SES light. The car has been running slightly hotter than normal (between 190 and 200 as opposed to about 180) since the SES has been on.

The car often smells like gas when it idles and she first replaced the gas cap because of the EVAP code but the SES is still on. I got under the car and the fuel lines seemed to be corroded from the filter on up to the front of the car. There's fuel leaking from the steel lines...not to the point of dripping but enough to coat the lines in places when the car's idling. This is a major issue that I'd like to fix before anything else.
Now, my first question is--how difficult would it be to replace the fuel lines from the tank to the engine?
The last work I did similar to that was replacing all the brake lines on my rusty-old-nasty 88 volvo and it wasn't terrible.
Also, I'm assuming that the fuel leak is why the gas mileage is terrible, but could it also be the cause of the slightly warmer running temperature?

Could the PCM be leaning out the fuel mix due to the amount of gas that's just evaporating from the tank? I've not run any codes on it myself because I don't have access to a code reader as yet but I'll have more details soon.

Thanks a lot,
WTS

Needing new fuel lines? From the filter forward shouldn't be too difficult to swap out. As for the SES take the car to an autozone they'll read the code for free. If your fuel lines are leaking then the evap code might stay.

For slightly hotter, could be the thermostat isn't opening up all the way. That won't be too bad. Fuel line from the tank to the filter will probably be somewhere around 60-80 bucks if you take it somewhere to have it done. (Having it done on my car on Monday, 60bucks)

Not sure about the SE's, but I believe the stock T-stat on the GTP is 195*.
If it's the same for the SE, which I would lean that direction, than your engine temps are normal.
Typically we install 180*(or colder) T-stats to help reduce the heat that assists in possible detonation on the Supercharged engines. Not a big issue on the NA 3800.

As far as the fuel lines I would replace stock lines with braided stainless with AN fittings ,leaking fuel can cause all kinds of problems and dangers best to be safe and not end up a crispy critter.Chico.