How do you change from Apollo gas heating system to electric heating system?

You contract with a licensed heating contractor who will changeover the system.

How do you change from Apollo gas heating system to electric heating system?

I'm not familiar with Apollo system, but if you'll clarify, it might not be too difficult for some of it as a diy job.

If you could point out what system you have from their website (http://www.apollo-hvac.com), we might be able to offer a bit more detail.

Don't know Apollo system, Gas needs to be safely removed and dealt with. Then. Hooking up the ducts, Running Safe and proper wiring. Charging the system. Good Electrician, and Ac guy can save Time and Money and even your life.
I would make quick access for contractor, help if they will allow. A customer can make a job easy or difficult,(cheaper or more expensive)