Ya that will charge it. You shouldn't need more than a pound, and if you do you've got a leak that shouldn't be too hard to find. I assume they'll use a UV dye so you should see it under a black light. It isn't a bad idea to have them do it, just make sure they are only authorized to do that. Sometimes they get people by either having them authorize all repairs and doing more than necessary, or by convincing you that you need more repairs than necessary..

The A/C doesn't really blow cold, its not an issue of it works 5-10 minutes then stops, right? Thats a different fix. ..

Also your volvo should be able to diagnose several problems on its own. To check if it has a code start with your car off (key in position 0) Then move forward to either I or II and look at the REC button on the climate control, it will flash one time if there's a code. If it flashes push the REC button twice, and only twice, when the light flashes and within 2.5 seconds of turning the key. The REC light will flash corresponding to whatever code it has. The code is three digit and the car will tell you one digit at a time. It is on for one second and then off for .5 if its counting up (so if the first number is 2 you'll have one second on .5 second off one second on) Then when it pauses for 2 seconds its switching numbers. After it finishes the first code (remember 3 numbers to a code) it will be 5 second delay between codes, if there's more than one. Therefore if you get the code 2-3-1 and 1-1-1 you'd have this sequence : 1s on, .5s off, 1s on, 2soff, 1s on, .5s off, 1s on, .5s off, 1s on, 2s off, 1s on, 5s off, 1s on, 2s off, 1s on, 2s off, 1s on ...