it depends on what you are planning on doing. What do you mean by [making changes]? I hope you mean adding new agents and DNs as well as routine maintenance! How many agents will be supported by this system? Also, you have to take into account the complexity of the system itself: will you be using only the basic framework or will you be also installing Inbound, Outbound, Reporting and other suites?
What I would suggest you do, is hire a Genesys consulting company to do the design for you, and then based on the design, either have sysadmin handle the system, or hire an additional support personnel.
Usually, when you install a system, you do not work directly with Genesys, but with VAR. Usually, VARs are people who probably sold you the PBX as well, so it is pretty convenient to have the same company do your PBX maintenance and Genesys support.
Here in Japan, we have over 100 sites, and on some sites admins do everything and on others, everything is delegated to the VAr or some thirdparty consultant. From my personal experience, I think the best combination is always a PBX/Genesys company, because usually when you have to play with Genesys, you also need to play with the PBX as well.
Do your homework, I highly advocate the CGE ( or any certification ) but remember certification at the lowest level is to study how a vendor implements their technology ( I.E. if you can study and comprehend then usually you can pass the test ) Be sure background is well rounded ( switching, systems integration, networks etc ).
My experience is that Genesys takes serious expertise to get setup and tuned properly. From that point on day oday admin is not a big deal, however, do not expect an admin to be able to make major strategy changes without serious risk of improper behaviour.
Genesys is an extremely powerful tool. It must be managed with care and thought.
You did not mention your choice of switch. Some switches are easier to setup with Genesys than others.