Going to vs Would

Woman:	I've just heard - my PhD proposal's been accepted! I'm going to start my research next year.
Man:	How exciting! How long is it going to take?

The woman has used going to because she's talking about future plans, that's things which are definitely going to happen. So the man also uses going to because he's asking for more information about the plans.

Now, we can also use going to, not just for certainties but for things which are probably going to happen. So, sometimes we use going to with 1st conditional sentences to express a strong possibility or probability. Here's an example:

If you drink the whole bottle of medicine, it is going to affect you very badly.

And that was a 1st conditional sentence with if and present simple with going to, which shows the likely result.

We can also use modal verbs and first conditionals, like this:

If you drink the whole bottle of medicine, it might affect you very badly.