I would stop the party for a moment and verify what you have. If you have a 19 mm hex head bolt securing the tensioner in place, as the M103s have, and mistakenly loosen an allen bolt holding the tensioner bracket in place, then attempt to tension/detension the tensioner with it still held tight, you are going to strip the threads on the tension adjuster. This is the 13 mm octagonal, long device sticking up at about 15 degrees toward the driver's side from vertical and directly in front of the coolant pump.
If you strip the threads on the tensioner adjusting device, you will now be into the r/r of the tensioner to remove this device and replace it. The bracket for the tensioner also has one bolt hole on the far left (passenger) side that is open to the engine and needs sealant to prevent a steady leak from beneath the bolt.
Someone with a scanner offered to send you ac section of the manual. If you don't have the manual, this appears to be very good advice for ensuring you know where you're going.
someguyfromMaryland who has been all over the tensioner and coolant pump on an M103 and doesn't want to see someone have to go there without a good reason