Skev,
You won't go wrong just chatting to the guys in the tackle shop at the lodge. It's in their interest to get you catching fish. As for flies, the selection in there is generally from Fulling Mill and Donegal Fly (both good brands) or some locally tied specials - they don't sell rubbish.
The size of it means that there are no 'hard and fast rules' other than those you'd apply to any trout fishing situation. Assuming you're thinking of bank fishing my early season
'if I had to pick one method' advice would be to fish small lures, slowly, on an intermediate line and concentrate your efforts from the fishing lodge to the dam or on the opposite bank over at Sykes Lane. Either can be good depending on which wind helps your casting most.
Given how local you are to the place, it would also be worth your while just visiting, watching and talking to anglers already fishing there. As long as you approach them as quietly as possible (and are mindful of their casting) any of them will talk to you, offer advice and generally make you feel welcome.
Don't be daunted by the size. Rutland is just lots of little bits of water joined together.