There is like a standard arrangement for EDM itself, and progressive house is no exception.
Start with your drumloop, give it like 32 bars - that's for DJs to mix in.
After that, break it down and introduce your melody and build up to your main part, again like 32 bars.
Drop it into your main part and give it like 32-64 bars.
Now, to keep things going, another break into another melody that differs completely from the rest and builds up to the second main part, again like 32 bars.
Pop the second main part, give it again like 32-64 bars.
Lastly unbuild everything and let the drums solo again (for mixing puposes), 32 bars, as usual.
With that rule you should end up with about 6-8min at 128 bpm.
Keep in mind that this is just a guideline, not the actual recipe.
When it comes to Instruments, listen to progressive house and just hear what's popular. Very common are pianos, saw-ish sounds and plucky instruments/sounds.
A good VST is Nexus2 by ReFX.
Effetcs should be nice cutoff automations, white noise, things like that.
Oh, yeah. Chords are normally minor. For chord progression, check out autochords.com, that should help a lot if you don't know much about playing piano.
Hope that helps