1. Dogs are not the only helper animals.
2. They can help blind people to get where they want to go.
3. They can help blind people to get to the place where they want to go.
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Q1 : Are they all grammatical?
Q2: Does #2 mean #3?
Q3: What is the part of speech of 'where they want to go' in Sentence 2?
1 and 2 are fine. 3 is very wordy (2 is far better!).
In #2, "where they want to go" is a noun clause serving as the direct object after the verb (infinitive) "to get".
http://www.grammar-monster.com/glossary/noun_clauses.htm
Q1: Yes, all three sentences are grammatically correct.
Q2: No, sentence #2 does not mean the same thing as sentence #3. Sentence #2 implies that dogs can assist blind people in reaching their desired destinations, whereas sentence #3 implies that dogs can assist blind people in finding their desired destinations. The difference is in the verb "get" versus "get to."
Q3: In sentence 2, "where they want to go" functions as a noun clause. More specifically, "where" acts as a relative pronoun introducing the clause, and "they want to go" functions as the object of the verb "get."