Learn Russian: Трудно найти хорошую работу в маленьком городе. - It is hard to find a good job in a small town.

This is an impersonal sentence. Russian doesn't use a dummy subject like the English 'it' in 'It is hard.' Instead, it uses the predicative adverb Трудно followed directly by the infinitive найти.

Could I use the imperfective verbs находить or искать here instead of the perfective найти?

Using найти emphasizes the desired result: successfully securing a job. If you used искать (to look for), it would mean 'It is hard to look for a job,' which changes the focus to the process. находить would mean it is hard to repeatedly or regularly find jobs, which doesn't fit the general meaning intended here.

English distinguishes between a town and a city. Does Russian have a specific word for town?

Russian generally uses город for both. To specify a town as opposed to a large city, you usually add an adjective, like маленький город (a small city/town) as seen in this sentence, or use the diminutive noun городок.

Why do the adjectives have such different endings: -ую for good and -ом for small?

They belong to different noun phrases governed by different cases. хорошую работу is in the accusative case because it is the direct object of the verb найти. в маленьком городе is in the prepositional case because it answers the question 'where?' to indicate a location using the preposition в.