Depends, how comfortable you are with the weapon. Have you had it down for cleaning?
If not familiar with the weapon. Take it apart where you have enough room to lay everything out in order as you take it apart. That way it's easy to get back together in reverse order.
Model 121 and Model 12 share alot of parts.
My guess would be you could after you get over the "why did I try this".
Since you have it apart might as well clean and inspect.