The OEM inner cam bearings should be replaced; they are not full compliment bearings like the Torrington/Timken B148s.
http://www.bigboyzheadporting.com/showthread.php?t=88
If you just want to replace the tensioner shoes, there are ways to do that without removing the cams from the plate but a special tool is required to roll back the inner shoe and remove it; some YouTube videos on that tool. Otherwise, the cams must be removed to replace the tensioners. There is a YouTube video of a rocket scientist that thought he could remove the tensioner without removing the cams and it is a very entertaining video if you want a few laughs.
The outer bearings need not be replaced unless they are pressed out of the bearing bores or pressed off the cams. The bearing that fell out need not be replaced if it has not been pressed off the cam; it will "fall" back into the bore with the cam. Apply some Loctite 660 to the bearing bore surface; a thin coat will do. Push the bearing/cam assembly back into the bore; you will have to align the inner gears and push both inner bearings into their respective bores together. If the other bearing is undisturbed, no need to replace it either. Google the "freezer/oven" or "heat/freeze" method for the R/R of the cams (with bearings attached); works every time and no special tools required. A Brit, Harley Hog, had a website with a complete video of the heat/freeze method but the MoCo shut him down a few years back. Pretty basic, freeze the outer bearings overnight; heat the cam plate in a 300* oven for about 20-30 minutes and drop the frozen bearings into the cam plate. Remove the inspection plug at the top of the cam plate before the oven; is has a rubber oring. Cams can be installed in the cam plate/bearings the same way; heat the cam plate, with bearings installed; freez cams overnight. Mock up the install setup first as you will need to have the cam plate level and secure; don't want it moving around. Install the inner chain; align the timing marks, and drop the cams into the bearing bores. You only get one shot at this as the cams will absorb the heat from the bearings pretty quick. Have done this plenty of times before I bought a small press. Only other way to do this will require a small press to press the bearings onto the cams and press the cam bearing assembly into the cam plate; should be able to find a YouTube video of the process.
You should have the service manual for your model. You will need a bearing puller to remove the inner cam bearings. Auto Zone used to rent a blind hole puller set which included the correct collet for the TC inner cam bearings. You can tap in the new inner cam bearings with a take off cam but as a one time fix but if you don't have one, George's Garage has the tool to remove and install the inner cam bearings.
If you haven't purchased tensioner shoes yet, don't bother to replace with OEM, replace with CYCO tensioners; you will need the CYCO tool to install the shoes onto the OEM holders.
http://twincamtensioner.com/
Read up on oil pump alignment before reassembly.