The reverse gear doesn't have syncros, most don't. It's not unusual for you to get a little grind going into reverse on any car. Two things you can do to minimize this is don't shift into reverse when moving at all (you shouldn't be anyways), and while holding the clutch, shift in to 2nd or 4th before shifting in to reverse. I've found that helps a lot.
As for the oil leak I would do exactly what you've been told already. Be sure to thoroughly clean the engine and underside of your vehicle off before you do this. Engine degreaser/shampoo is the best to do it quickly and easily...most everything you need off should come off with that and a quick spray from a hose. Typically you want to take the car for a drive immediately after you've done that and put the dye in. Get the engine up to temperature, drive a good 10 miles or so, then check it again. This gives you a chance to try and find the leak before it's sprayed all over the place and made it MUCH more difficult to pinpoint.
And remember, when checking with the UV light and glasses on (please don't be supid and burn out your retinas), all coolants (as far as I know) will react to the UV light as well and light up. Be sure you're finding the dye in the oil and not spilled or leaking coolant.