well I just did two mpc300 and did the 1st all doors closed,no cables or fax as normal and loaded as it should.
Did the 2nd with side door open and same as the 1st.
the only thing i wont pull is the glass and optics..
And I DONT PULL ANY FUSERS NOR DRUM as an added caution..
i can wait the extra 5-10 minutes...
plus i dont rip apart anything till i power up machine after finishing the FW load..
do a test sheet or config page and then take apart..