I would not replace the 1C03 transistor unless it is proven to be defective. Solid-state components do not wear out or degrade, like electrolytic capacitors eventually do, so they are not normally replaced if they are working.
One of the speaker connections will be routed through the 'phones' jack (so the amp is quiet when using headphones).
If it is through the 'tip' connections, that would go to the speaker (+) terminal. If it is the 'sleeve' connections that disconnect the speaker, then that would be for the speaker (-).
If you can post a picture of the trace side of the board in that area, it should be easy enough to figure out.
One of the speaker connections will be routed through the 'phones' jack (so the amp is quiet when using headphones).
If it is through the 'tip' connections, that would go to the speaker (+) terminal. If it is the 'sleeve' connections that disconnect the speaker, then that would be for the speaker (-).
If you can post a picture of the trace side of the board in that area, it should be easy enough to figure out.