Salesforce development work

Salesforce dev work where we are looking to create a record from XML & additionally use rest API and web service to ultimately send a search query and return results.

The use case is an external web site will have a button which allows a user to connect to a Salesforce org (potentially via OAUTH though guidance would be appreciated). The button on the website essentially generates an XML output and need to create contact records in Salesforce for the user, up to a max of 50 contacts from the output.

Additionally, looking to enable the external web site to access Salesforce data, by 'searching' based off a pre-defined search string by the user. It is envisaged that the user has a string (which contains the search terms) and this somehow connects to Salesforce and retrieves any matching results and sends them back to the web site.

The development for the external web site is not required in this job, only the Salesforce development side and documentation on what input/output is needed to facilitate this, and the documentation can then be provided to the website developers to 'plug into'.