1) Yes, you can max out both professions. In addition you can also max out fishing, cooking and first aid if you so choose.
2a) You can do so if you are only trying to raise your skill. But you cannot have two items added to the same piece of gear. When you add the new item it overwrites the old one. For example, if a player has an armor patch on a piece of armor and then has it enchanted, the enchantment will replace the armor patch. But the game asks you if you want to do this before doing so.
2b) See 2a above.
3a) It depends on your profession. For skinning your resources are extremely common. For herbalism it can be fairly common, depending on the zone you’re in and if you are trying to find a specific type of herb. For mining they’re less common, but you can find them if you run around rocky areas.
3b) Again, it depends on what you’re doing. Skinning isn’t a problem. Herbalism and mining, it just depends on who sees the dot appear on their mini map and gets to it first. Mineral nodes that appear in caves can be a bit more competitive, but the same still applies.
4) It depends on what profession. Gathering professions do not have a character level restriction. But by their very nature they don’t really need one. Its unlikely a level 10 character would survive long enough to gather herbs in a level 60 zone even if he had 300 herbalism. Production professions, such as blacksmithing and alchemy, do have restrictions. Apprentice requires level 5, Journeyman level 10, Expert level 20 and Artisan requires level 35.
For more information about professions:
http://www.worldofwarcraft.com/info/professions/basics.html
Edit: Removed an oops. :- )
Edited, Thu Jan 20 16:39:30 2005 by Calabar