Old post, but here is my answer anyway:
Yes, but probably not easily.
First, most old germanium transistors are pnp and most modern silicon transistors are npn. You can't reasonably substitute npn for pnp.
Next, the bias setup will probably need to be adjusted. The base bias voltage is around 0.3 volts for germanium and 0.6 volts for silicon.
If you have a circuit diagram it will help a lot. If not, its going to be more work.
You might want to see if you can identify the transistors and try to locate some NOS somewhere.