A -  Export Accounting entries from Odoo to Sage 30, 50, 100 :

use this OCA addon https://www.odoo.com/apps/modules/8.0/account_move_line_report_xls/

- export your selected moves, save the xls file as csv. the use "import paramaétrable" in sage to import entries. I am using it , and it's working well with sage 30, 50.  ( needs some minor code modifications on date format )

B - export invoices from Odoo to Sage

use this OCA addon  https://www.odoo.com/apps/modules/8.0/exportsage50/

C - importing data from Sage to Odoo, is more easier since you can export any thing from Sage in .csv format. It' sup to you to map columns with odoo models with odoo's import wizard.