Hi, Dave, and congratulations on your new toy!
Now, wobbly lens is normal... shutter release... in what sense is it loose? As long as it works, it's better loose than stuck!
Now, regarding the batteries, there's an entire body of work about whether the current 1.5 V batteries overpower or wreck the meter. Nothing of that happens and your meter will give you correct readings. You can use regular PX625 batteries (available at any local Wally World) for the camera meter. BTW, this is a shutterspeed priority camera, which means that your meter (which is a needle) will set the aperture according to the shutterspeed you choose. If the meter decides there's not enough (or too much light) for a good exposure, it'll block the shutter release button.
Use this camera with slow film. Superia 100 or Reala are great, but don't shun filters, which come in handy on sunny days. Also, avoid using faster film (like ISO 400) on sunny days, as the camera's highest shutterspeed is 1/500 and it won't be able to handle the light.
Now... check the seals. They maybe a bit gunky, but that's not too much of a problem unless you have light leaks.
Further information... click on the link that will make your heart beat faster: the Canonet G-III QL17, for a nicely scanned manual of this camera.
And now, for you to have an idea of the things you can do with this magic wonder... Take a look!