Is it permissible to work with my maternal uncle in guiding European tourists, and is the livelihood earned from this work unlawful?

It is not permissible to work in a profession that involves unlawful acts. For anything whose عمل (performance/doing) has been forbidden, it is forbidden to consume the wealth or benefits that result from it. It has been authentically reported from the Prophet, peace and blessings be upon him: "Fear Allah and be moderate in seeking (sustenance), and do not let the slowness of provision lead you to seek it by disobeying Allah, for indeed, what is with Allah cannot be attained except by obeying Him." And whoever abandons something for the sake of Allah, Allah will compensate him with something better.