Since Aiff is a non comressed format, and since the TTM57 records digitally, if I record something, and then record it again, am I losing quality?

For example, let's say I use an instrumental to make an intro on a song, and record the finished product and leave it in AIFF form, then later, use that version in a mix, thus I have re-recorded a recording. Will I lose quality?

Depending on how you set your gains or pitch control etc., then yes it will change / degrade the quality slightly - but probably less than playing the same thing through a dj cd player and re-recording it.