The spool gun to use with the MM175 is the Miller 3035. I've used that setup for 4043 and it is hard to get good penetration without burnthrough - also keep in mind the cleaning process. The spool gun is preferred to use over a liner because it's so difficult to drive the aluminum through for that length.
You can practice and get to the point where your skill may be sufficient for the project, but be prepared (based on the lack of practice time working with aluminum) to trash a lot of work.
The preferred method for working with aluminum is tig, but it takes a long time to perfect, is an expensive process, and can take a long time to do correctly.
Keep in mind this is only a thought, but if you don't feel up to burning a ton of aluminum, you may want to consider laying everything out, labeling everything precisely, then taking all the bits to someone that does a lot of work with aluminum. This way they could mig it up real quick, you'd likely get it the same day, and you may even hang out to make sure everything ends up the way you want. The key thing would be to use a lot of clamps to make sure everything fits well together before you take it over.