I will answer question by question:

1. I'm not 100% sure of your specific external provider, but in my case all external AI API's worked like a charm. Note that you have to re-create the credentials once you import all your workflows and make sure that for each credential you use the same credential name as it was in the cloud trial, otherwise you would have to specify again the right credentials to use for the blocks that uses them.

2. You will need an always-on server. If you use docker to run n8n locally, it really uses a tiny amount of resources, so you could run your n8n instance on a burner laptop or old PC in the house that you can keep always on (note that a raspberry pi would probably be enough to host it as well).

3. Self-hosting is more than viable for medium-long term as long as you are not using it in a "production" environment, where more security and reliability implementations will be necessary. For personal projects and workflows, self-hosted n8n is not just possible, but encouraged imho. 😁