Well my friend, you sound like operating an Odoo Community 17.0 on your own.

The biggest difference between Odoo Community vs Odoo Enterprise is that Odoo Community is a perfect development framework for business application and Odoo Enterprise is the full feature ERP based on that framework.  And the framework by it self is not doing much for upgrading it from a version to an other.

There is 2 ways to upgrade you Odoo 17.0 to 18.0, the first one is to convert your Community to Enterprise and use upgrade.odoo.com to upgrade your db from 17.0 to 18.0.

The other way is to wait for OpenUpgrade (an open source project of the OCA) to be ready for upgrading Odoo 17.0 to 18.0, dont expect something before may or june if you have a lot of module and you might have to migrate a part by yourself (your module and other custom modules).

In a case or in the other, you will have to remove a few add-ons you did add to emulate enterprise features.

Strongly suggest going to Enterprise, but we can help in both case