Ok, for anybody having problems installing maps on the "Map" program I figured out how to manually install the maps provided by Navicore.
I'm sure most of you already know this, but I'm stupid and had to learn the hard way.

Step 1: download the map from the navicore website to a PC (link to site provided in a previous post).

Step 2: Unzip or unpackage the "(map you downloaded).tar.gz" file. If you are using winzip you may find you have to unzip it twice. Both ".tar" and ".gz" are compressed file format. It's like they the zipped an already zipped file. So if you unzip once and open the folder to see a ".tar" file, unzip again.

Step 3: Once it's completely unzipped down to a directory starts with "mapdata_(location)" in my case it was nested down a few folders. Copy only that directory not the any of the previous directories.

Step 4: Find which SDcard has a directory called "map" and open it. Paste you copied "mapdata_(location)" into that "map" directory.

Step 5: Open the "Map" program and click on the top left corner of the window to get a menu. Select "Maps" in the menu and if the map you installs shows up with NO "????" by it you more then likely did everything right. If you do see "?????" try something else.

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What not to do....

Do not try and put the file on the SDcard if not unzipped all the way, and rename to some like "mapdata_USA West" that crashes things.

Do not copy the first folder when completely unzipped thinking that's right one, navigate to down into the subfolder till find the one called "mapdata_(insert your location)"
copy only that folder.

Within the map program don't select the map to display if you see something like "??????? 0mg" that will just make the program crash every time it tries to starts.

If for some reason the program does crash after all this the first thing to try before deleting the whole "map" directory is to only delete the directory called "mapdata" NOT "mapdate_USA East" or anything like that, only the one called "mapdata". If it still crashes uninstall the program and then delete the "map" folder. The uninstall will not do this automatically. Re-install and forget about this post.

Actual tarball doesn't contain compresssion algorithm, it is used as container to preserve file structure, permissions and so on.

Compression with gzip and bzip2 has been added nowadays to ease the use, but afaik the tarball is compressed after "tarring", and result is identical when compressed with separate program. File extension may be tgz or tar.gz, but it's all the same.

To elaborate a bit more detail, from my own experience:

tar - Tape ARchive - archives files, directories and properties into one 'solid' container -- nothing gets compressed, just archived. It was really designed for backing up everything onto tape and letting the hardware do the compression in the old days.

gzip - GNU zip - compresses a stream of data or one or more files (but it doesn't compress multiple files or directories into ONE archive--it just touches each file you tell it to compress and then leaves behind a compressed version).

bz2 - bzip2 - Like gzip, it compresses, and also like gzip, it only compresses a stream of data or one or more files but doesn't archive multiple files or directories. The advantage of bzip2 is that it compresses MUCH tigher than gzip. The disadvantage is that it also runs a lot slower and uses much more memory.

To get the best of both worlds, you tar up a branch of files and directories, then feed the tar file (or the stream of data that the tar outputs) through gzip or bzip2 and the result is a solidly compressed archive of files and directories in one single file.