On tupping ewe lambs you have received good advice already : it's not for a novice sheepkeeper.
I would add that, as a very experienced sheepkeeper and lamber, I would never, ever use a tup that's a larger breed than the ewe's own breed for a first time (whether the ewe be a lamb - ie., will lamb at one year old, or a shearling - ie., will lamb at two years old), and recommend using either the same breed or a smaller one, and if the same, make sure it's one with narrow shoulders. Others will add, get one with a small head, but my own experience is that it's not usually the head that causes the problems (although it can be relevant in horned breeds where the male lambs have developed horn buds at birth.)
In common with a lot of farmers, especially breeders of very meaty types such as Texel and Beltex, we keep a Shetland tup for our first timers, no matter what breed they are. Shetland lambs come out running, are very weatherproof, know where the milk bar is and how to get on it, and are very persistent. So even an inexperienced ewe usually ends up feeding her lambs without assistance, and you rarely get birthing problems with a Shetland tup.
We also keep a larger stock tup, so our Shetland tup is a naturally polled one. (They do arise, but are not common.)