I can answer a few of the more technical questiond for you, from looking at the screenshots. I am basing this information on Rugby 2005, which looks remarkably similar to the Cricket 2005 screenshots.
However, I did nothing on Rugby 2004, so I can't tell if Rugby 2004 and 2005 have similar file tyes, etcor whether they are new for 2005 - except for the .big files.
- TV Overlays.
These will not be editable apart from the little EA logo on the corner, and the team logos. You will not be able to edit the positions of the scores etc. These appear to be identical to the Rugby 2005 ones, and we haven't found out how to edit them yet, as the format is a tough nut to crack.
- Gob File
There most likely will be a .gob file, but it will be editiable with EA Sports Big Editor (a third party program for editing FIFA and such-like). It will actually be a .big file, just renamed. This is easily enough edited, but the file names are likely to be all messed up and therefore hard to work out which files need to be edited.
- Texture Editing
The textures are likely to be stored as .fsh files, which are easily editable, given the correct software. Check out The Rugby Forum for information on editing Rugby 2005 graphics.
- Other information
To apply a patch to the game, it is most likely that you will just need to put the replacement file (extracted from the .gob and edited) in the Cricket 2005 root directory.
- Player Editor
If indeed there is one, it will more than likely be a stripped-down version of the FIFA 2005 player editor. I'm not sure about player sizes. In Rugby 2005 there were only 4(!) body types allowed, but Cricket 2005 may adpot the more typical "Height/Weight" method of creating the skeleton.