Dear Sir, i have 4.5 years of OpenERP experience, i started my OpneERP career from OpenERP's india development center and worked there for 1.5 years as an employee after that worked with OpenERP partners and now from last 2 years working as freelancer, and have successfully completed several projects and implementations so far. Related to your requirement, i have done OpenERP integration with Magento, Prestashop, Amazon, Ebay , and also with private custom developed applications. so i have enough experience to deal with various API. i quick check on purolator website to find API documents, but looks like its available to registered merchants only. overall i understood your requirement, except one point "Print delivery labels directly to the a thermal printer quickly" is this to do from OpenERP, ? because OpenERP is web based it can not access printer directly, please let me know
Regards
Zahir