I want to change from running conventional oil to synthetic and want to make sure I don't hurt anything. Should I change the oil once, run the engines for a while and change it again? Will that be enough to been sure I got out all of the old oil?
Any other suggestions?

the old oil won't hurt anything execpt make it (the new) oil dirty quicker...the motor may use alittle oil as the syn washs away the other deposits from the old oil it will stop when the new oil builds its deposits

RUN THE SYN...