1. Remove seats from car
2. Gather all necessary parts together
3. Take to local upholstery shop and have them do job for you. If they tear the cover, they own it.
They will have the know how and tools to do the job correctly and if they don't have to take seats in and out, price is usually much better. It should be about $125-$150, depending on your area and that would include all new padding, supplied by the shop. Check the prices of the padding kits alone from Big 3.
I HATE upholstery work, so that's what I did and they came out perfect in one afternoon of work. I did not need covers, just new padding.
And don't forget the headrests if you have them.