Totally agree that the final power transistors are toast. Before replacing these transistors and trying again, you should figure out a little about the speakers. What impedance they are - do they have a little transformer on them - how are they wired together? As to your fried receiver, is it a stereo device? The 10 speakers were probably one circuit instead of two if they are 20 years old. You probably will need to rewire the speakers into 2 channels/circuits of approximately 8 ohms each - depending on your receiver. (bet you didn't want to hear that)
As to fixing the receiver, I would pay for an analysis and estimate for repair before doing anything unless you are experienced at trouble-shooting. If it is only the power transistors that blew, you can replace them easily. They are usually silver, mounted on a heat sink (metal bracket with cooling fins), about the size of a quarter, have a white gue underneith, and mount with two sheet metal screws. If the thing is totally gone, be sure your next receiver has a protection circuit to prevent this problem.