Re: Using 48khz sample rate with 4...
In the Audio Bin, if Logic doesn't automatically convert your audio files to 48Khz, you can select them and choose Copy/Convert files... Keep all the settings the same but change the sample rate.
It's important that the sample rate of all audio files used in your project match the project's sample rate... otherwise they will playback at a different speed.
I'd like to make one point (you might prefer to skip over as it's my opinion).
Why are you going to record at 48k?
I only record at 48 if my project is destined for film/video or has been specifically asked for in that format. Otherwise, IMHO, the benefits of recording at 48 for a CD project that needs to be converted to 44.1 anyhow are minimal.
Also, Logic's Apple Loops can act a little weird when used in projects of higher sample rates... Can't remember if that's just for 96k or if it affects 48k projects too...
Sorry if it feels like I'm raining on your parade... I don't intend to discourage you from trying it out and finding what works best for you!