Disc brakes aren't that difficult to sort out and maintain.
Firstly, if the lever feels spongy or they are pulling too close to the bars then they probably need bleeding. The method can vary depending on the type of brake you have. Before bleeding though it's worth checking weather your levels have reach or bite point adjustment.
If you do need to bleed the brakes then you'll need to make sure that you are using the correct type of brake fluid.
Magura and Shimano use mineral oil while most others use DOT 4 or 5.1 oil.
You don't need to replace the brake hoses when bleeding unless they are badly damaged.
It sounds like you may have Quad brakes, which I think use DOT 4 oil. Post up a photo to confirm this.
A major factor in performance will be whether or not the pads and rotors are clean.
Any oil or grease on the rotors will find it's way onto the pads and contaminate them too. This will cause horrible brake squeal and poor performance.
You can clean the rotors will Isopropyl Alcohol or disc brake cleaner (same thing), but contaminated pads are best replaced as they are almost impossible to clean. You can also roughen the surface of rotors with emery paper to improve braking.
For pads I always use gold sintered versions for long life and good all weather performance. Resin pads are good in dry weather and kevlar pads are great but generally expensive.
If you remove the pads, the pistons won't just fall out of the calipers. Be careful not to pull the brake levers though while the pads are out as the pistons can be pushed out this way.
There are loads of useful videos online for bleeding your brakes and I can also highly recommend this website for bleed kits, parts and instructions.http://www.epicbleedsolutions.com/