Yes, I've bought several guitars from the US.
Shipping: get them to ship with UPS or Fedex, because both of those companies will handle the package end to end, are fast, reliable & offer decent tracking & insurance. If they ship via USPS (=US postal service), it gets passed to Parcel Farce over here or some tinpot local courier who will do their best to break it.
Packing: make sure the seller loosens the strings before packing (assuming it's going by air), that the guitar is securely packed in its case which is in turn surrounded by padding & in a box.
Import tax: you will need to pay import duty & VAT on your purchase. Last time I imported a guitar duty was 3.7%, then VAT (@17.5%) goes on top of that. So, for example, if you paid £1000:
(1000 x 1.037) x 1.175 = 1218.48, so VAT + import duty will be 218.48 (there's often a £10 or so admin fee too)
Another good selling point of UPS & Fedex is that they take care of the paperwork for you. UPS will expect a cheque or card on the doorstep, Fedex will invoice you later for it.
Hope this helps.