This is how I replaced the LCD in a fairly new Garmin GPS device. The thing is not designed to be consumer serviced so it was a huge pain - likewise I couldn't find any information from other people who have been through the ordeal. Everything begins on ebay, where there were several vendors selling replacement LCD's. Be sure to get an LCD + Digitizer combination, it is likely to cost somewhere between $30 and $60.
Here is the damage:
I was happy with the replacement kit - it came complete with some special screwdrivers. Specifically a very small philips screwdriver (which was actually too small) and a star shaped one that was needed to even start.
The first step is to crack the front open. This is not for the faint of heart and will take significant force and prying. There are tools for this type of thing but I used a sharpened flathead screwdriver. Expect to break a couple of the tabs. There are some cables that go between the two halves but you shouldn't need to worry about them.
Here are the cables you need to remove, they're slotted so you don't need to worry about putting them back in the wrong way:
This PCB is attached to the LCD with a flexible cable so remove it carefully. I found that prying here dislodged it at which point it could be gently removed. The audio port and a little tab in the lower left are primarily what holds it in place.
Make a note of how this one is oriented, tweezers will help getting it back into place:
Almost there, just need to remove this plastic middle piece:
More prying is required, expect more damage to be done:
At this point I found out that the seller had sent me the wrong part. Note: It was the part he said he was selling, but Garmin changed what LCD is used. Fortunately he was able to source the part I needed and swapped it out with no questions asked - Just had to wait a few weeks for the round trip shipping back to Hong Kong, which turns out to be less than $3 for a small box. About a month later and I'm back in business:
Just a matter of putting everything back together now. The biggest issue is getting the flex cable seated correctly, you will need to have the LCD removed from the frame and the flex cable completely extended. Make sure its seated squarely, I had to take the whole thing apart a second time thanks to this mistake!
Getting the frame on is also a puzzle, you can feed the PCB through like this. Be sure to get the red and black cable plugged in when seating the PCB.
You're basically done now, just snap everything back together and plug it in!