Thread

I hate to say it but we are running ExpressionEngine v 1.6.5 and we feel like we need to update it.

Problem is our site is very large and I am a little afraid of any change.

Can someone tell me if updating to the latest version of EE from our version would be seamless all things considered?

It would be good first upgrade to EE v1.7.1 and then upgrade to latest EE v2.7.2.

As you mentioned that your site is very large and you wouldn’t like to effect anything on running website so it would be good to make a staging server where you can do upgrade process.
Once everything in upgrade process has been done successfully, just migrate the upgraded site having latest EE version.
I always follows same approach and rarely get issues.

No, it will probably not be seamless.

Upgrading from EE1x to EE2 is usually an involved project.

You’ll need to inventory the current EE1 site, and any/all add-ons used to create it. 1x Add-ons had to be re-written to work in EE2, so if you’ve used anything that the author didn’t update you’ll have to determine if EE2 has the functionality natively or if there is an alternative add-on available.

Is your site “large” because of the number of templates and code, or because of the amount of content in the system?

It’d be a good idea to copy the old site to a developement server while the upgrade is being one. That way you can iron out all the odd bits and peices before cppying back as the live site.