Hellou.
Im programmer and front-end developer with 12years experience specialised in osCommerce stores.
During that time i was moderator and administrator on bigest polish osC forum.
Here, on freelancer.com i have made many updates and tweaks for older osC versions.
I would be more than happy to offer migration to osc 2.3.4 (also in responsive version) .
To give you detailed price and timeline id like to know the addons you have / want to move to new version.
All the best,
Trygon eXtreme