1. How do you remove a shower /tub enclosure. It's a stock fiberglass tub enclosure that you see at any Lowe's / Home Depot warehouse. I'm concerned about removing the enclosure around the drain and the faucet/showerhead area.

2. I want to build a tile (shower only) enclosure in the space. Can the drain, which is located by the wall below the faucet/showerhead area be used as the drain area for the shower only or do I have to move the drain to the center of shower floor base.

If you are going to toss it all away, you can remove the handles and escutcheons and then cut through the fiberglass around the faucet area. The drain screen probably screws into a removeable fitting, using a drain wrench. You'll have to cut the drywall back a couple of inches to find the nail flange. You can leave the original drain IF you can properly slope the floor to the drain. Is this slab or frame construction? How about a fiberglass/composite drain pan and tile walls? Pans have right, left and center drains.

I removed the shower handle,face plate,and spout leaving the cartridge in place in the off position. You will have to solder copper pipe to move the shower valve to a higher position. Use a pair of pliers with the handles inserted in the drain and turn with a crescent wrench.
I cut the surround ound with a dewalt rotary cutter using a ceramic tile cutting bit. Set the depth to the width of the drywall and follow the edge of the surround to expose the flange. You can cut around the nails and then pop them loose with a screwdriver and remove with a hammer. Cut the rest of the surround into small pieces for easy removal. The bottom is the hardest since there may be boards glued to the base.
I ordered my swanstone retrofit base through Home Depot for $155.00.
It's a lot of work.
Here are some pictures:
http://www.roomzaar.com/rate-my-space/Bathrooms/Pattys-Bathroom-Remodel/detail.esi?oid=539170