If you change a profession that gives you like skinning a + to crit or herbing (a hot) or mining a + to stam to something else you lose that
same with jc/lw/bs they all have at top lvl things that prof gets and only that prof you change you lose them
edit--Leatherworking is the crafting companion to skinning; with it, you can turn your various kinds of leather into an assortment of items. Most of these will be leather armor, of course, of a variety of types, with a number of items that’ll give good agility bonuses, which are perfect for hunters and rogues. In addition to the armors, the main support items are armor kits, which can be applied to four different kinds of armor to permanently enhance their defensive capabilities, and quivers or ammo pouches, which all hunters will find necessary.
One of the main drawbacks of leatherworking is that it will become precipitously less useful after your hunter or shaman hits level 40, since they’ll be able to switch over to mail at that time. This is more of a problem for a shaman than hunters, as the latter will be primarily concerned with pure stat bonuses on their equipment rather than its capabilities as armor qua armor; shamans, though, will need both the higher armor of mail as well as the strength and stamina bonuses that are more readily found on that type.
Unlike professions, you can obtain as many of the secondary skills as you wish, even if you already have two professions. These skills revolve around creating or finding items that will let you more easily heal yourself; they’re not usually highly lucrative and won’t let you create equipment or long-term buffs. http://www.mmonice.com
bull...leatherworking can make mail items matter of fact some of the best pre raid mail is from lw...learn the game before you talk