If you have a Local Fish Store worth their weight in salt (no pun intended), they can order you a complete top frame for a standard 180. A guy in my area just had one ordered in at my LFS. Took a week. It won't matter if it comes from Marineland (Perfecto) or Aqueon as they are the same dimensions. Just one more reason to shop local over chain stores.
You should probably plan on replacing all of the bulbs in that fixture except the LED moonlights. You can replace the LED if you want but it is not needed and you (and your fish) won't notice the difference. I'm gussing those are double end halide bulbs so I'm not sure what your options are but shoot for something in the 14K range. Those will be a crisp blue/white. 20K if you want more blue. The power compacts can be either daylight (white), actinic (blue) or a combo. Bulb replacement will run you some coin so before you commit to that you may want to weigh that cost against a new fixture. Halides and CFLs are perfectly fine but together they will run hot (as mentioned). You do not need to repalce any bulbs until you add corals (assuming you will eventually) so this is not something that must be done now.
Are you going to run a sump on this? On a tank that size, I highly suggest that you consider it. Drill the tank now or buy a hang on back overflow box.
Congrats on the house and welcome to saltwater!!!!