Repairing a broken screen glass can be very expensive project to do.

Finding a dealer that will change the glass is not a problem, but the price they charge is just really too much for the work and the spare parts is how to do that on your own and making it cost a fraction of the price AND mostly it can be done in under 15 minutes.

The phone used to demonstrate this is my wife's Nokia Lumia 625. The screen in this one cracks very easily. My 3 year old brother dropped it on the floor from about 30 cm height and it just cracked. The main reason to this is that the glass goes over the phones plastic edge so nothing is protecting the glass.
First thing first.

Where do i get a replacement glass for the phone?
Well, i think it's time to check out what eBay has to offer..

Okay. Now we have the spare glass.

There is not really much tools that you will need. You will need a screwdriver (the ordered glass had one for free inside!!) and a 100% plastic playing card or something that is as thin.

Step 1. Disassemble The Phone

The screwdriver was not the only free item in the box. It also had that blue plastic flap. I don't remember the name for it but it is used in disassembling for plastic parts since it wont leave any marks.

Taking apart the phone is in this case is very easy. Just remove the back plate and then take the screws off.

After that use the plastic flap to pry the phone open. Search for a small "holes" in the sides and push the flap in there. It will crack open. Then remove the battery and the touch screen cable. Remember the position of the cable for easy remove of the glass. Mostly it's on top of the phone.

Step 2. Remove The Broken Glass

This is the hardest part. Do this wrong and you wont get a picture ever in your phone.

If you have and TFT or LCD screen in your phone the risk is not big. BUT if your phone has got an LED display like AMOLED or any other type of LED screen be very careful. If an LED display is touched with any force it will break.

The glass is attached to the phone with two side tape from the side of the screen. Remove this and the screen will fall out.

To remove the tape and separating the glass from the phone can be done with plastic playing card. Yes, you heard me right. The playing card is thin enough to fit between the phone and the glass and its hard enough to cut the tape in there. Start by inserting the card in the lower corner of the phone and start pushing it inside.

Most safe method in this is when you have the one corner free put the playing card sideways and start swinging it in. Work your way up as you feel the tape is giving up.
I used only one playing card to remove this glass it's good to have few spare in the reach.

Step 3. Insert New Glass

Well done! The screen is now off and the phone is waiting a new one. Remove as much old tape as you can from the sides of the phone so the new glass will fit on the phone neatly remove the inner protection film from the glass. Remember that removing this will also remove the film from the tape in the new glass.

Push the glass touch screen cable trough the phone before pushing the glass on the phone.
Put the cable in the correct place and insert the battery on the phone( in this Nokia the battery is inside the phone).
Test the phone that it still works.

Step 4. Assemble The Phone

Assembling the phone is just the reverse as before. Put the screws back in and hope for the best.

The phone works fine and the glass is smooth AND most importantly the touch screen works like a charm