The best way to empty a pool is with a portable water pump, they have small pumps that can pass 2280 gallons a hour (small 43cc 2 cycle motor and pump). You can buy one or they have them to rent at hardware stores and tool rental places.
OR
Use the pool's existing pump. Set the spider valve to waste and the suction to pull only from the main drain.
If your pool is above ground it does not matter, But if your pool is in ground and you drain it it will act like a boat and float if the water table rises.
You should never completely drain an above ground pool. The chemicals in the vinyl liner that allow it to stretch when originally installed do not last. If you drain the water, the liner will shrink and when you refill the pool there is a good chance that instead of stretching back the liner will rip instead. NEVER drain your pool.
If it is a vinyl liner pool you have to use a submersible pump. You can get a small one for right at $100.
You have no choice but to replace the liner
Regarding pool: a liner refers to an in-ground or above ground pool that uses a Vinyl Liner to hold the water. The liner is a custom fit to the shape of the pool, in-ground pools utilizes steel, or composite walls to hold the earth back and the floor can be a thin concrete or a sand bottom.
Vermiculite
To fix a detached vinyl liner from its spot on an above ground pool, the water will have to be drained from the pool. Then, a marine patch can be placed on the area to re-attach the vinyl to the place where it came apart. Allow this to dry thoroughly before refilling the pool.
With a Vinyl Liner you should not empty it OR take it down. It's very hard to get the liner back in place if you remove it. Vinyl shrinks as it ages so you also need the weight of the water to hold it in place. Movement of the liner could also cause older vinyl to crack. Think of an older cars dashboard! To winterize the pool you should lower the water just below the skimmer, plug the return line, drain the skimmer, pump, filter and plumbing and cover the pool with a winter cover.
You need to remove the old liner. Leaving the old one will cause the new one to retain moisture between the layers and rot the new vinyl and rot the walls of the pool.
Be more specific please- what about removing it? cost? difficulty? What type of pool is it? fiberglass? vinyl liner? concrete?
No
You loose some stability.