Yep, you are on the right track.
I would go with 15x8 wheels with 2.5" back spacing. 15x10 is a little too wide. Go with 32" tires.
The Sky pads are already drilled for 3/4" forward and I would do that for the front axle. I believe that I run two 3/4" spacers on the front driveshaft to add the needed length-one at the t-case end and one at the diff. Works just fine.
I would source the brake lines from Sky as well as the other components.

My rig is the second one in this photo and it has a basic SPOA with 32" tires on a 15x8 2.5BS rim. 1" longer shackle in front/2" in the rear. Works pretty well and it flexes enough for me. The only thing I wish I had was another 12" in wheelbase.
Yes, you will need gearing. The 6.5 trail gear case works well with 32" tires. If you only have the stock 1300cc engine, you might need some additional gearing in the form of diff gears-probably in the form of 4.625 Sidekick gears or the Yukon equivalent. Start with the t-case gearing though.