A1. An "ideal" hash will spread the strings uniform-randomly over the hash space (2^32). If you have 1000 strings, then your probability of collision in that case is approximately
1 - exp[(- 1000 * 999)/(2 * 2^32)]
which is small (about 1.16e-4), but may not be negligible in your case. Your chosen hash may perform as well as that, or a bit worse, or a lot worse, depending on your input space.
A2. You can do this pretty quickly. From the reference below, if you pick a bit over 77000 strings, you will have a better than 50% probability of finding a collision. It'll take you a few minutes to write the code, and probably less than a second for it to find a collision.
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