Long time since I used VMWare, moved to linux machines and VirtualBox, but there will be similarities.
Which distro to use: If you look at
http://www.distrowatch.com there is a list of popular versions and you can follow links for information to end up at a download location.
As well as the actual distribution - Ubuntu - Mint - Fedora there are options for a "Desktop Enviroment" (DE) which as well as how the thing looks, will affect how much resources are used.
From the regular Ubuntu Trinity, fairly heavy on resources to lightweight LXDE.
I do not know how much memory your Mac has but say 4GB then maybe you can afford to allocate 2 GB to a virtual machine. Perhaps VMWare will decide for you, but do a little checking first.
For ease of installation along with Gimp already installed, I advise Mint with the MATE (DE) Since your VirtualMachine less than 4GB memory 32 bit is ok. Mint has a good and friendly forum with lots of advice.
Download the "live" DVD iso - tend to be on the big side these days 1.5 GB - such is life. Hopefully VMWare will allow directly using the iso as a virtual disk rather than burning and booting from a physical DVD drive.
This example, trying out the new Bodhi 4 - a very light on resources DE on an ubuntu base but not for beginners. That shows the virtual DVD drive but lots to configure from the amount of memory to sharing folders, with the host machine.
http://imgur.com/mWlO9zKYou might not succeed first time round, but the virtual machine is just a set of files in a folder. Delete and start again.
edit: looks largely automated
https://vimeo.com/117362745and for the tools
http://tutorialforlinux.com/2014/11/17/ ... ual-guide/