1. Yes. You can use write erase to remove the config. If you need to delete the VLAN’s, delete VLAN.dat in the flash. Remember 9800 runs IOS-XE so it will mostly behave similar to a Catalyst switch (Not 100%)
2. I would say just get rid of the wizard. Do the basic config via CLI. Then access the WLC via GUI over the in-band mgmt or service port. Most probably you cannot access it over the GUI is because http server in WLC might not have enabled by default. In any of my deployments I haven’t used day 0 config wizard. Below is what I will do
1. configure the Gig 0 (service port) and switch uplinks. Create L3 SVI’s for in-band mgmt.
2. enable http server and authentication for http server.
3. create user credentials and enable secret (priv 15)
4. add default routes for global and mgmt vrf. (Service port is mgmt vrf, so without the route you will not be able to access)
5. configure line vty access.
6. Disable both 2.4 and 5 radios globally in the WLC and set the AP country and the re-enable the radios. If you want to skip GUI configuration wizard then this step is compulsory.
7. set wireless management interface. (Only 1 supported in 9800 platforms)
8. Set ntp and time related stuff.
Once you make sure that the controller is accessible and working as expected, the you can start hardening the controller and start the wireless configuration part.
