Newbie 75 gal. tank build/ upgrade

Ok first off I joined this site recently, figured better to be on a local site than one where everone is from california or somewhere 1000 miles away. I got into this hobbie about a year ago when one of my wifes friends was getting rid of her 55 gal tank, it was givin to me and little did I know at the time what I was getting myself into. The tank was very neglected one clown fish in (he was yellow at the time)it the live rock was was covered with muck no working lights a skimmer that wasn't pluged in, oh man if I knew then what I know now I would have done things very different. The day of the move It was just empty the water and live rock out temps were very cold outside so rushed it to the house put rock back in fish and top off with salt water, Big mistake!!! nothing but problems ever since should have totaly redone the whole tank, which brings me to the 75 gal. build, lets get it right the second time and have a great tank sitting in my living room that everone likes to look at and turn the 55 into a frag tank or something of that sort. There is alot more I could say but this is getting to long already.


So I have aquired a 75 which I will be drilling here in the near future (hopefully the back is not temperd)so I can add a sump and get rid of all the unsightly HOB equipment, this is where I could use some advise, if i remember right 1' pvc will drain 1100 gph which will be ok for this 75 correct? I plan on using the herbie metehod and a 1200 gph overflow box from brs, going to a 30 gallon sump which I will also be building, now do I have to use a submersible pump? I have a sequence pump I bought for a koi pond build that I never used dont know if it will work or not. Now for the return do I want 2 of these and what size? this is where I am going to start is there anything I am missing for this part?

 

Ha never mind on the sequence pump it's rated at like 3600 gph