Would a comma be needed before, after or both of the word "hopefully" in this sentence?

Solution 1:

'Hopefully' is being used as a parenthetical expression to interrupt a thought and not as a conjunctive adverb joining two sentences.

Since it is functioning as a parenthetical expression, you need to punctuate it with two commas.

"...and, hopefully, become a member of the band."

Solution 2:

Your bare infinitive "become" is dangling in the air. One does not know where your bare infinitive belongs to - the reader has the choice of two verbs plan and learn and you make the reader try to find out how you constructed this sentence.

That is no good. I would choose the simplest and clearest formulation: ... and I hope to become a member of the band.