Answer
Decrease. Increase.
Work Step by Step
If you tunnel into a uniform-density star, your weight decreases. The gravitational attraction of the mass above you partly cancels the attraction of the mass below you. This is discussed on page 171 and shown in Figure 9.23.
If you stand on the surface of a shrinking star, the mass beneath your feet stays the same, and you get closer to the CM. The force increases.
