97 AC not very cold, can I DIY by adding charge myself?

I suggest having someone take a look at it for you. The AC system is a closed unit and unless there is a leak, shouldn't ever need recharging. Both the new cars and your 97 take the same R134 refrigerant. There are many parts to the system and my question woudl be is it blowing cold or not blowing cold.

I agree with a couple of people on here, do not try to charge the system yourself. If you don't have a problem, you will, and if you do have a problem, you'll make it worse.

I am not doubting your skill level, but the statement is correct, to much causes the compressor to fail, to little and you don't get the right cooling. the gauges that a tech uses are expensive, and that is for a reason, in order to be accurate. In all, the money you think you'll save will cost you later.

I am all for people doing things themselfs and saving money, this is not one of them.

+1 for having an AC or repair shop do this for you. If you have to ask how to do it, DON'T. I have seen way to many people hurt themselves, or damage equipment trying to save themselves the labor cost by DIY on the AC. We're not stating that the OP is stupid or incompetent. It's just not worth freezing a hand, or worse yet, an eye, or blowing the compressor, or a refrigerant line. R134A or R12 instantly freezes anything it comes in contact with, including you.

I used to work for a chain auto parts store, which will remain nameless. I got fired one summer because people that came in had no clue how to service the system, much less find the low pressure port. I refused to sell refrigerant to these people. I didn't want to see them hurt themselves or others. Whatever you end up doing, don't even DREAM of charging through the high side of the system. You'll wish you hadn't.