Today, I will need to wash the car, clean the air conditioner, and resealing the driveway.

Correct sentence: Today, I will need to wash the car, clean the air conditioner, and reseal the driveway.

One of the rules for writing with parallel construction is to ensure that verb tenses agree within the sentence. In this sentence, the verbs "wash" and "clean" are written in the future simple tense; so too should the verb "reseal" be in future simple tense.

The college will be closed on Monday, Tuesday, and on Wednesday.

Correct sentence: The college will be closed on Monday, Tuesday, and Wednesday.

Within a sentence, care must be taken that the proper prepositions precede a noun or phrase. Here, the preposition "on" applies appropriately to each day of the week; thus, there is no need to use another "on" before "Wednesday".

Working as a teacher is not only difficult but also is very rewarding.

Correct sentence: Working as a teacher is not only difficult but also very rewarding.

In this sentence, the correlative conjunctions "not only" is placed after the verb "is"; the correlative conjunction "but also" is placed before the verb "is". To correct the parallelism in the sentence, the conjunction "but also" should follow "is". However, repeating "is" is unnecessary, as the verb "is" serves the entire predicate.