Ons gaan die monteerinstruksies en onderdelelys na.

No. In this sentence, gaan is not a future marker. It is the finite part of the separable verb nagaan, which means to check, to go through, or to inspect.

So:

• Ons gaan die monteerinstruksies en onderdelelys na. = We check / go through the assembly instructions and parts list.

Compare that with a real future construction:

• Ons gaan die monteerinstruksies en onderdelelys nagaan. = We are going to check the assembly instructions and parts list.

That difference is very important:

• gaan ... na = present-tense form of nagaan
• gaan nagaan = future construction with gaan
  • infinitive

Because nagaan is a separable verb.

In a normal main clause, the verb splits into two parts:

• the conjugated part goes into the usual verb position
• the particle goes to the end

So:

• dictionary form: nagaan
• main clause: Ons gaan die monteerinstruksies en onderdelelys na.

This is similar to other separable verbs in Afrikaans, for example:

• opstaan → Ek staan vroeg op.
• inpak → Sy pak haar tas in.
• nagaan → Ons gaan die lys na.

Not by itself, no. Here na is not functioning as an ordinary preposition. It is the separated particle belonging to the verb nagaan.

So in this sentence, you should understand gaan ... na together as one verb: nagaan.

That means you should not translate na word-for-word here. Its meaning is built into the whole verb.

Yes. Die is the Afrikaans definite article for both singular and plural.

So:

• die instruksie = the instruction
• die instruksies = the instructions
• die lys = the list
• die lyste = the lists

Afrikaans does not change the definite article the way some other languages do. It is simply die in all these cases.

Because one definite article can cover both nouns when they are linked by en.

So:

• die monteerinstruksies en onderdelelys

means that both nouns are definite. English does the same:

• the assembly instructions and parts list

You could repeat die as well:

• die monteerinstruksies en die onderdelelys

That is also grammatical, but using just one die is very natural.

They are compound nouns, which are very common in Afrikaans.

monteerinstruksies

This is made up of:

• monteer = assemble
• instruksies = instructions

So the whole compound means assembly instructions.

onderdelelys

This is made up of:

• onderdele = parts / components
• lys = list

So it means parts list.

Afrikaans often joins these ideas into one word instead of writing them separately.

Because they refer to different kinds of things.

• instruksies is plural because instructions usually come as a set of steps
• onderdelelys is singular because it is one list

So the combination is perfectly normal:

• the instructions
  • the list

This is also very natural in English: the assembly instructions and parts list.

A very common past form in Afrikaans is the perfect with het.

With separable verbs, the past participle is usually written as one word again:

• nagaan → nagegaan

So the sentence becomes:

• Ons het die monteerinstruksies en onderdelelys nagegaan.

Notice the pattern:

• present main clause: gaan ... na
• perfect: het ... nagegaan

Good question, because separable verbs behave differently in different structures.

In a subordinate clause

The verb usually appears together as one word at the end:

• Ek dink dat ons die monteerinstruksies en onderdelelys nagaan.

In an infinitive with te

The verb splits again:

• Ons probeer die monteerinstruksies en onderdelelys na te gaan.

So the patterns are:

• main clause: gaan ... na
• subordinate clause: nagaan
• infinitive with te: na te gaan

This is one of the most important patterns to learn with separable verbs in Afrikaans.