Saftey issues aside, if you've never welded aluminum, this is not the place to start.
Aluminum is tricky since it melts before it gets red hot. It's really easy to heat it too much and have a big hole fall out.
If you intend to do it yourself, plan on several months of practice with scrap pieces before you attempt the tank.
I will repeat "safety issues aside." However, when I went to welding school at the community college as a 60 something senior, I was started off doing TIG DCEN on mild steel. I did that for about 3 Saturday sessions and grabbed some AL out of the scrap bin, set the machine to A/C with a pretty even balance and lit up. Sure, I messed up for about 10 minutes. But hiding from the instructor in the booth, I worked myself into it before the day was out. And that was going back and forth to steel. Same tungsten, just a bit duller.
I wanted so bad to try the pulse, but I didn't know anything about setting up the pulse frequency, background and balance. I don't know about several months of practice unless I wanted to be some hero in a fab shop stacking dimes around corners and such.
Besides, I'm so tired of the exaggerated dime stacking that I appreciate an old school smooth weld more so. I say if Skyking has the proper equipment to go for it. At least give it a go on scrap.
Safety issues in consideration. Remember that is all has to be super clean. If there's **** in the existing weld or metal, it will be **** weld.