Road Trip: New Hampshire

New Hampshire is known for its sap houses, which start with MAPLE and end with SYRUP. Can you figure out the words in between, and then calculate the mystery letter?
Hint #1: Putting a word in parentheses scrambles it.
Hint #2: Putting a letter in brackets converts it into a number from 1 to 26.

M + (related girl) + S = unrelated girl
A + (general waste) + Y = more specialized waste receptacle
P + (time period) + R = request to above
L + (gold) + U = island party
E + (book) + P = wrap around

gold: [u] _
book: _ _ _ [v] _
related girl: _ _ _ _ [w] _
general waste: _ _ _ _ [x]
time period: _ [y] [z] _

[u] + [v] + [w] + [x] + [y] + [z] = [ ? ]