Hey there.
You should be able to connect and use an SSD with that computer. The only downside that I can think of, is that the computer probably has SATA II ports, which means that the speed will be limited to 300MB/s (instead of 600MB/s for SATA III) and most SSDs have speeds of 400-500MB/s. So you won't be able to use their maximum speed. However, regardless of that, you'd still get a quite noticeably faster system by using an SSD as an OS drive.
About the maximum capacity, you shouldn't have issues with any of the SSD capacities that are available now, but please note that some laptops and desktop computers sometimes have incompatibility issues with larger SSDs. The best way to find out what would be OK is to contact the computer...