Please tell me more: are you training on water, or are you training on land?
Around my house I have lots of motivational posters about rowing. It is to always remind me that no matter how hard the training is, rowing is always fun, and I am always striving to do my best.
There are different types of training in my experience, depending on whether you are rowing indoors or outdoors. If you are rowing indoors, I would suggest that you do sprints 500m and try and get a personal best, or sometimes I do a "rowing marathon" and I row for 30 mins non stop.
If you are rowing outdoors then I would suggest you to do different types of training like land training (eg push ups, running around, etc)
If you do it properly (put 100%) then you'll find that your body will be dead after training (for example I couldn't walk down the stairs without wobbling after being on ergs for 30 mins), but after that you body will get used to it - you'll grow muscle and get stronger over time.
Yeah, stretching is very important. I always seem to forget about it though. Which isn't very good, since that means that I would wake up with cramps in my legs the next morning or when I'm walking to school.
Are you planning to train on land or water? Before you go on the water or get on a rowing machine you need to have an understanding of good rowing form. Once you understand the proper form you can apply it on the water or on the rowing machine.
I think an important part of training is supplements. I have been taking one for over a year now and feel it is very helpful, it is called DIM. DIM helps you to get more out of your workouts because it maximizes the benefits of a workout!