All you have to do with the neck glue is wipe it off with nail polish remover or acetone (avoid painted areas).
I would been thrilled to have bought a Big Top for $9 as she's one of the more popular twins and both of mine have much serious issues than glue or a hair trim.
So congratulations on your pony! I bet she's beautiful!
The #1 reason why we collectors get aggravated about QC in G4 currently is because it's ALWAYS been this way. G1s have lots of flaws straight from the factory and we have had to put up with it for 30 years. We've just learned how to resolve/deal with issues over the years.
So don't feel about starting with G1s and expecting really nice ponies... most of them have flaws too! *pony hugs*