Is there really three moods in Spanish (indicative, subjunctive, imperative)?

ARE there three moods/modes in Spanish?  No, there are four:  indicative, subjunctive, conditional, and imperative.

As for how long it takes to learn it, that depends on your foreign language aptitude/talent and the amount of time you can devote to working on it.

Yes, there are three moods in Spanish: indicative, subjunctive, and imperative.

As for the conditional, it is somewhere between a mood and a tense. "The argument in favor of calling it a 'mood" is that mood is based on a definition as something like 'the use of verb forms to grammaticalize modality' (where modality is  defined as the expression of a combination of notions including possibility and obligation that essentially mark something as "not a straightforward assertion of truth')." Whew!

The amount of time required to "learn" a language depends on many variable factors: your grammatical knowledge of your native language, whether or not you have previously learned other languages [Spanish is one of the easiest for an English speaker to learn], the quickness and confidence of your learning style, your "ear" for language in general, the degree to which you plan to delve into grammar, and perhaps most importantly, your motivation to acquire this particular language. It is worth devoting at least a year to, but as you continue to use it, you will learn more and more about the language for many years.

You mean 'are' there really three moods. Yes there are really 3 moods in Spanish.

How long it takes a person to learn it depends on how good they are with languages and what type of course they take.

yes there are, lets take the verb decir, to say. The indicative in englih would be "I say" which in spanish is "Yo digo". this is mood is the first and most important to learn in my opinion. The subjunctive is used when you're not saying that someone is definitely doing something for example "It is important that I say" in spanish is "Es importante que yo diga" In this example we are taking the I form (conjugation) of the verb decir in the imperative then switching the o for an a, as you would for all spanish verbs that end with er or ir. (for verbs that end with ar you would switch it to an e ending, like habla to hable). then finally for the imperative this is the command form. for most verbs, all you have to do for this is remove the last letter off of the infinitive (which is the verb in the to say/to do/to be form). Except decir is an irregular verb where the command is "di". But for the verb comer, "come" means the command eat. So really after you have the 6 forms of the verbs memorized which is I, he, she, we, you guys, and them (slightly different for ar, er, and ir ending verbs) and you have the irregular changes to the verbs down, then all it takes to know how to use ALL of the other verbs is knowing these kinds of patterns. It took me about 2 years to learn to learn this much + other spanish vocab but i was only 14-16 at the time so it will probably take longer if you're older

+edit= The conditional is the easiest one to learn and its the would tense. you just add ía to the end, or ías if its for the you form íamos if its we, íais for you guys and ían for they. there are some irregular changes to it though for a few verbs like decir which would be diría(I/he/she/it would say). But most are like comería which is simply "to eat + ía".

Yes. Those exist in English, too.

You should see a doctor. Indicative.

I recommend that you see a doctor. Subjunctive.

See a doctor! Imperative.