Thes best I can tell you is that on my monitor and based on what some others have posted with their flat screens you should have the full range of resolutions available to you with VGA. The HDMI may or may not give you all of the same choices. (as on mine where the highest resolution is only available with overscan) When i first set up my system it automatically went to 1600x900. I do not recall if it was different when hooked up to VGA, it was too long ago.
There are a number of threads on here with different people using different size and model flat screens, with various successes and failures. Should you run into a problem when you do get to hook up the system (hopefully you won't!) it would be worth checking out those threads as well. Maybe even do a little reconnaissance and bookmark a few of the threads after doing a search so you don't have to do it last minute. I know, the threads are too numerous to count but sometimes a little advance research can go a long way when you are pressed for time.
Good luck, let us know how you make out.