I would have an initial worm count done, including counting for fluke. That would give you an idea what you are starting with. It really depends on how much and where you are grazing your goats (i.e have there been sheep on the goats pasture in the last 12 months before the goats arrived?). I get worm counts done about twice a year for the goats, once in autumn (still to be done this year - ooops) and then again 10 days AFTER their routine worming dose post kidding.
So far my goats have not shown any sign of fluke, whereas the sheep (in a different field next to the river) have shown fluke (and now get routinely treated twice pa with Fasinex), but so far not had any problems with worms. My vet advised that sheep (and presumably goats) do not build up resistance to Fasinex, so a bottle can last you a while. I have only just finished my first one, bought in 2009 and with best-before date of early 2012. The smallest one you can buy is 750ml, and my current one has a best before date of sometime in 2014. Just make sure it is stored away from frost.
My goats however do need worming, I have found that white wormers don't do the job anymore, and am currently using yellow ones. Might have to switch to Ivermectin based ones next year.
There are no wormers or flukicides licensed for goats (maybe except Panacur, but not sure), so the same withdrawal period as for sheep will apply for meat, if you are milking and no milk withdrawal times are given it is usually 7 days minimum for human consumption. Also please note that for most wormers (I do not know about flukicides) the goats dose is about 1.5 to 1.7x the sheep dose, but if you are unsure post on here and someone will give you an answer if your vet is not sure. Panacur can be up to twice the sheep dose without any danger.
To estimate your goat's weight, measure her girth, and I have posted in the past somewhere in this section a table with girth measurements to corresponding weights, if you can't find it - I have got a table on paper, so can always look it up for you.