I would not say it's easy, but there is really no use in scaring you at the point you are most excited about the project.
But ERA puts out a decent manual and if you read it and follow the instructions most people can get the job done.
There will be countless issues and challenges as you go through it, but evidently you like that sort of thing or you'd buy a regular car. My best advice is to ask questions here when these issues arise. Most likely someone here has had the same issue and can help.
Having ERA assemble the car to the extent you have will save a lot of time and some mis-steps.
Here are some tips I've thought of:
Get the big fan if you are not going to run the front fans.
If you are considering undercar exhaust and the outboard brakes rear suspension there are issues you need to be aware of. PM me or read my site.
Chuck