2001 Chevy Venture wheel allignment or wheel bearing

I recently had an oil change and was told I needed a tie rod end and a wheel bearing replaced. I asked what was of immediate concern and was told tie rod (with no allignment, though) Since that repair was done, the van shimmies (vibrates,shakes) whenever I am on the highway (doing at least 100km) Do you know what is causing this?? Thanks!