I am looking to rollover money from an employee sponsored trust (old employer) to my new retirement fund. I am also looking to withdraw a portion. how can this be done?

My previous employer sent my 401 to a JP Morgan Chase trust. I am looking to rollover the funds into my existing 401k with Transamerica with my new employer. I am also looking to withdraw a portion of these funds for personal use. Any tips on how to begin this process and what tax issues I may encounter?