Sonicwall pro 200 netgear router and some confusion

Alright guys, I'd like some input on a few things.

I picked up a used sonicwall pro 200 on CL to learn more about hardware firewalls/rules, etc . My current topography is motorola SB5120(modem) > NetGear WGR614 (router - I also have a WGT624 thats not in use at the moment) > additional 5port switch > computers on LAN

So I put the firewall after the router SB5120 > WGR614 > pro 200 > switch > LAN computers. First off, is this correct? I would have figured the firewall would go after the modem but before the router to prevent any outside attacks from seeing the router and possibly disabling it. Would it be suggested to go modem > firewall > router > switch? If so I'm assuming I would enable DHCP on the firewall and just disable it on the router, effectively making it an AP.

How would I go about securing the wireless aspect of it? I've cracked enough networks to know that most all consumer grade stuff is pretty weak. I figured if the AP is compromised the firewall wouldnt prevent access to the hardwired computers, pretty much useless. Right? (This was my reasoning for putting the firewall after the router)

I'm super intrigued by networking/security and start my bachelors in CS specializing in security in a week but we dont get into the good stuff till atleast late sophomore year and I didnt want to wait that long before taking the next step.

Thanks!