hello , im new to this forum but i thought i'd share my 2cents. Ive been a vegetarian for over 5yrs and vegan almost 2 (and loving it =] ). i dont have problems with my weight and im mainly using this website to help me improve my health and get leaner.
my main tip when turning to veganism would be to make sure you are not finding replacements for all the animals products you eat. When making the transition it can surely "help" but you may be setting yourself up for failure specially if one of your goals is to maintain/lose weight. Most replacement foods specially nut pates, soy cheeses, etc, are packed with fat and so it can be easy to lose track of your fat intake. So i'd recommend to go straight into less processed more whole foods, lots of fruit and veg. Like it was said above get a recipe book and read many of the amazing blogs u can find online.
Last and not least, veganism is a way of life, so if you have a reason (animal welfare/ morals/ethics towards eating animals)why you are doing this it will always be much easier to keep up. =) Good luck!