1-Only in Record Mode you can see the db meter when sampling. There are no digits to know if you are clipping but from my experience, if the threshold bar is moving at the far left of the screen, then the sound is gonna be low. If the bar extends toward the middle of the screen then you'll be ok. If the bar extends all the way to the far right of the screen and not moving much, you gonna have clipping galore. However, for that real loud, clear and hot sound, the bar should cover 3/4 of the screen and only tapping the far left screen occassionally. Once you master that db meter, you'll always will have a hot sound.
If you desire to monitor a song's levels meaning not just samples themselves but the whole track, then I suggest in Record Mode, to switch it to Main Out for resampling and you can see how far the bar is going.
2-Most basic set-up for the 500 is a DJ mixer (preferably with EQ) and a sound source (turntable, keyboard, CD player, iPad, etc) and speakers (active speakers are great but passive monitors will do if on a budget but you will need an amp).
For iPad, you gonna need a little portable audio interface like iRig or something. Though they don't really intergrate, the iPad will be like a DAW recording the MPC500. You can sample stuff from the iPad via headphones.
