New to sump systems.......on the right track?

Well I personally would return the sump you just bought as those cost a real pretty penny.. Then keep everything else, you could just get a spare tank and silicone some dividers and you'll have tons more room for media, socks, and heaters/pump. Those sumps easily run 300 dollars and a diy sump costs less than 100 if you can scope a good tank on craigs. The sump doesnt have to be huge but I would recommend a 55 gal at the least.

The problem I have noticed with those sumps is that the foot print is pretty tiny... I have a 35 gal sump the same style as the aqueon sumps and I find the pump running dry after 5 days at only 76-78 degrees. A lid does help but that model 4 is also a 35 gal and evaporation is going to be a pain in the butt. The only reason I havent switched over to a 55 gal or a 75 gal is because I cant fit it under the stand through the doors lol...

And I think you'll find your going to need a larger pump and a 55 gal will allow it. If you do keep the one you bought and try adding a 2400 gph pump you'll find out why I dislike them. It runs the sump dry and to compensate you must add more water. Once you get the sump topped off and god forbid the power goes out or you unplug it, your going to have a flood.

The pump and overflow should be just fine. Depending on your 1200gph pump will lose 2-5% of its max flow per foot of height. So it should work out, but if it doesnt you could just drill a bigger hole in the overflow and get another bulk head or just plain out buy another overflow box! lol But your flow should match up perfectly from the overflow box to the pump.