I would think you would have to find your own way up to site, thats the impression we got and hired a car for the process.
As for the NIE I'm not sure the literature they sent out says...
"Polaris finance department is willing to help you obtain your NIE from the local foreign office in Murcia, free from any management fee, but the administrative fee, which is stated on 15.70€ for this year. Polaris will pay this fee in advance and this amount will be charged in the utilities settlement.
Polaris has negotiated with the foreign office to do all the administrative formalities on your behalf. Once the NIE document has been issued you will be required to collect it personally at the local foreign office (Av. Ciudad de Almeria, 33-Edifico Volante-Murcia). The appointment to collect the NIE will take place a few days before the signing date of your property."
Polaris customer service tel no. - 0034968012090
Ps : Let us know how the snagging goes. Are you completing next week as well?