Major slope is sort of a non-specific term. Could you elaborate on that more? You may end up wanting to excavate part of the slope and move some of that downhill in order to create a larger level area. If that method is more practical - compacting the now loose dirt becomes very important. If the slope is less major - you can cut into the slop and have the entire pool be on undisturbed soil (which makes for a good starting point for a good foundation). The key in making the determination really lies in how deep the pool will be in relationship to your finished height (assuming a deck or similar structure for access). If your deck height is 48" and the slope drops more than that over the width of the pool you will need to extend your flat region to make up the difference. If the slope drops less than that over the width of the pool - then you should be able to fit it on undisturbed ground.

Getting past that - you will want a retaining wall of some form too. This will work to keep the excavated portion from collapsing in on your pool. There are a lot of different options for this - though you should keep in mind that many municipalities require the wall to be engineered if it is taller than 3 feet. This can add a few hundred dollars to the overall cost just getting the stamped drawings. If you are outside of a region which has more stringent building codes you will want to look closely at what options you choose even if you don't go with an engineer. South Carolina has some whacky soils in places, make sure you don't skimp on the retaining wall just to get the pool in under budget.

Once you get all of that squared away - most of the above ground pools which I have helped with installing were pretty DIY friendly. The actual setup usually pretty quick, though it may take a bit of time to remove any rocks, roots or other stuff (we found the fender of an old car when prepping for one). After that - sand, compact, level, sand, compact, level and bring in the pool kit.

Regarding the warranties, no specific experience with them - but I understand they are a bit like the warranties on shingles. That is, the first year they have a full warranty against manufacturers defects and then each year after that it is prorated based on the expected life of the product. If the pool had a 10 year warranty and cost $2500 - at the end of 5 years, they might reimburse you $1250. You want to document your installation process and follow the manufacturers instructions to the letter - not doing so generally gives them an escape from their obligation.

Also along those lines, during my career in the residential construction business I have seen more companies offer new products with 10, 20 and 30 year warranties go bankrupt after 5 years than I can count. Most of the time it is just before a known defect becomes widely known (various Masonite siding companies jump to my mind here). I haven't paid that close of attention to the above ground pool industry - but I would guess that similar practices exist there as well. In other words, don't count on a warranty (long or short) as an indication of quality. Rather, look for something which is standardized so that when the original company goes out of business you are not forced to completely replace a component that might otherwise have been repaired.