I was unaware how confusing my little tutorial for hacking savestates was until a few people emailed me saying so, and I'm very glad they did. Below is a simple tutorial that helps you change a mobile suits experience, it is a direct copy of my reply back to an email. Here is a very rough chart with the needed experience for each level up which you can see here.
First off you're going to need a fairly good knowledge of Hexadecimal and a Hex Editor. I recommend Hex Workshop that you can get at http://www.bpsoft.com/. The dollar sign's are just there to signify that the offset is in hexadecimal format. All of the following information is based on ZSNES savestates. The EXP points are located at 2452 (for the Gundam) and 2454 (for the Guncannon) and 2456 (for the Guntank and the second Guncannon). Now for an example. Say you want 1000 EXP points for the Gundam. First open up your hex editor and go to 2452 (that's in hexadecimal). Now we'll need to convert the 1000 into hexadecimal. One of the reason I recommend Hex Workshop is because of its decimal to hexadecimal converter. You should have gotten a value of 3E8 for the 1000. Now you'll need to split that 3E8 into two pairs of numbers, if a number doesn't have 4 digits then add a zero in front of it (3E8 becomes 03E8). After splitting that up (you should now have the two pairs of 03 and E8) flip those and combine them again (your new value would be E803). Write that number down and go back to your Hex Editor (which should be at 2452) and type in the E803 but make sure that you overwrite the numbers there and don't add the E803 in because it may cause the savestate and rom to screw up the next time you play it. Now save and make a back up copy of the savestate (in case by some strange occurance it messes the savestate up you'll have an original copy to go by). Open ZSNES and load the ROM and then the savestate and go into your menu for the Gundam and see if its EXP is at 1000. I hope that this helped you. If not be more specific about what you are having trouble with and I'll try my best to help you in any way I can.