I installed a Moss-sourced vinyl top by myself on my TD without any major "Aw *&%&%^%$" moments. Fortunately, there's several "How-to" guides available for the T-series MGs, and it was quite straightforward with no surprises. Read the instructions, take your time, measure twice, etc. I'm sure there's lots of "how-to" info for your ride. "Classic Motorsports" magazine recently had an DIY article on installing convertable tops on late model MGs.
Cloth or vinyl? Consider the historical context of your car. MG's - "Cheap and Cheerful", Big Healeys - definitely upscale manly sporting machine. In my opinion, high-end cloth tops on MGs goes against the image of the breed, and vinyl on a restored Healey - not right, either.
Other issues to think about - vinyl is much easier to clean, but gets stiffer in cold temperatures. Cloth looks fabulous, but a pain to clean. If you leave your LBC parked outside all the time, the vinyl would probably fail sooner, but who does that anymore? What's the condition of your paint? Pairing a high-end cloth top with over-the-hill body paint would be a bit much, unless a re-paint is in the near future.
Just my two pence worth! Whichever top you choose, the car will look good 