What area to use for the lift/drag forces
If you're using equations with $C_L$ and $C_D$ you need a (single) reference area, $S_{ref}$:

$$L = q_\infty S_{ref} C_L$$
$$D = q_\infty S_{ref} C_D$$

For aircraft this is generally the wing planform area. However, for a satellite, wings aren't going to be of much use, so the area upon which molecules will be impinging (such as the nose cone or cross sectional area normal to the flow) would be a more useful choice. Your coefficients will vary depending on which area you choose. Note that it really doesn't make sense to try to model the "lift" of a satellite.

On that note, satellites, especially at altitudes as high as 500 km, are essentially ballistic, so the ballistic coefficient is perhaps a better choice:

$$ BC = \frac{M}{C_d A} $$

Here $A$ is the cross sectional area of your object, but for all intents and purposes it's very similar to $S_{ref}$. We can substitute it back into the drag equation to get something useful for satellites:

$$ D = \frac{q_\infty M}{BC} $$