hi Mike,
the hardest thing about switching out the pump is simply removing it. That 1/2" clear tube coming up from the pump has a black plastic elbow where the water returns into the tank. Just pull the elbow attached to the main tank wall, back into the sump. It is connected by a 1/2" line that goes down to the pump. If you pull up on that 1/2"tube and the power line, the pump will come right up.
You might consider using Maxi 900 instead of the 1200 for in the tank. The 1200 uses 20W of power for 1110 gph, the 900 uses 8.5 watts for 870 gph. Watts=Heat. More than a few people choose the 900 for just this reason.
I'm still using the stock pump in the sump and it's weak. I'm awaiting two Maxi 900's. One will go in the sump, and the other in the tank for recirculation. I ordered a Hydor FLO
http://www.marinedepot.com/md_viewItem.asp?idproduct=HD01401
I'm going to overclock the Hydor FLO (by putting too much water flow through it), but can you really trust the directions? It will go on the in-tank pump to spray water all over the tank. And since I'm getting extreme, I ordered a Phosban Reactor to replace my home made unit.
http://www.marinedepot.com/md_viewItem.asp?idproduct=TL4311
I couldn't decide if it would be better to filter out phosphates (to keep algae down) using some type of phosphate soak material, or carbon (to reduce the organics). Someone asked, "Why not filter out both" and provided this link for Seachem Seagel Filter Media
http://www.marinedepot.com/aquarium_filter_media_seachem.asp?CartId=
"Hey!" I thinks to myself..."surely this is a better mousetrap"
I will hang this unit external, next to the Remora, and it will use the cheap pump that came with the unit. I don't need big flow through this unit.
Also, since there will no longer be a carbon restriction in the return line, more water will flow through the sump.
So that will be my next addition next week. Rats, I'm running out of space to hang things on.
So...
1. Cheap pump that comes with the tank will circulate water into carbon reactor.
2. Maxi 900 will pump water out of the sump into the tank.
3. Maxi 900 in tank will have rotating collar to increase circulation..all the days of it's life.
4. I will marvel at this great wonder.