if you need your information during the repair the best thing would be to remove the drive and mount it in an external enclosure....... and use a bootable Linux distro to access your information...... and back everything up to a FAT32 drive so file permissions are not an issue later.
esp since until you do it, a disk image is not a guaranteed to work kind of thing....... if a new logicboard is installed windows "might" not like it and you may have to call microsoft to re-validate your license.
As far as cloning the drive and applying that image to the same size hard drive clonezilla would work. ( i have used clonezilla on multiboot OS systems before)..... a bigger drive would still work, however without using advanced features of OSX's command line diskutil or another partition tool...... resizing the OSX partition might be an issue......unless you just want to copy your drive for temp. access while its in the shop?
anyway you can clonezilla it and using Linux to mount the freshly cloned drive get your data......
I assume your taking the drive out to get the data since the laptop won't work with a graphics chipset failed cloning/imaging would be hard with any program since you can't see what your doing
So removing the drive before sending it in for service might be best, and Linux will read all the partitions. (read only mode to be safe and you will have to deal with file permissions later for any files you change.
If your lucky and the data you need is on the OSX side and you have remote login on you can SSH into the mac......... SSH requires command line experience and i don't know if you have that.
If remote management is on too, you can just remote the entire machine with VNC.
Sorry if non of this or just some of this makes sense.......tired..... just options i could think of before and after repair which exceeds the scope of the question.