I I think I can rally to the point of view that "craindre" is a formulation somewhat too strong, specially as "concerned (that)" means "worried". Instead of this construction something along the line of the following might be preferable.

• Je me soucie du fait que cela pourrait être difficile. (less strong)

• J’ai dans l’idée que cela pourrait être difficile. (still less strong)

II This particle is called "ne explétif", which means that it conveys no meaning; it can be removed without changing anything.

(LBU 14ième édition § 1023) Lorsque le locuteur sent dans le contexte une idée de négation, il
introduit parfois dans les propositions conjonctives un ne que l’on
appelle explétif, à la fois parce qu’il peut toujours être omis et parce qu’il
ne correspond pas à une négation objective. Ce ne est donc facultatif,
même si les grammairiens ont essayé de rendre son emploi plus rigide.

• Je crains qu’on NE me trompe (La pensée s’arrête sur
  l’idée de n’être pas trompé.)

Translation by user LPH When the speaker becomes aware of an idea of negation in the context, he/she introduces sometimes in conjunctive clauses un ne that can be called "explétif", so called both because it can always be omitted and because it corresponds to no real negation. Therefore, this ne is optional, even though grammarians have tried in the past to make its usage more strict.

• Je crains qu’on NE me trompe (The speaker’s thinking focuses on the idea of not being cheated.)

It follows that this sentence has the same meaning as the following.

• Je crains que l’installation soit difficile.

Craindre is certainly usable (although some might consider craindre to be a little too formal here):

Je crains que ce soit difficile.

and you can also use the more mainstream avoir peur:

J’ai peur que ce soit difficile.

The translation you got is also perfectly idiomatic although slightly more formal:

Je crains que l’installation ne soit difficile.

You are bothered by the ne because it’s a ne expletif that doesn’t convey any negative meaning. In casual spoken French, you usually drop it:

J’ai peur que l’installation soit difficile.

Another way to express the concern is:

Je me fais du souci à propos de l’installation.