Characters with the Enchant Magic Item ritual or the Alchemist feat may craft items of the associated type of their level or lower, although the cost to do so is equal to the normal cost to buy the item. The advantage of the feat/ritual is in flexibility, as you can craft things on-the-fly instead of needing to plan ahead.
For example: You could buy a Flameburst Crossbow +2 for 3,400 gold. But then you end up in a Lava Golem's lair and feel all kinds of silly when you could use Enchant Magic Item before entering the lair to make a Frost Crossbow +2, pay the same gold, and be ready to tackle your enemy's weakness.
These can be improved by things such as the Mark of Making Dragonmark feat or the Master Crafter feat (and I believe the Artificer class also gains some benefit, which you could gain access to after chargen with a multiclass feat).
D&D 4e doesn't really have rules for "repair," but magic items don't really break except for story reasons, anyway, and by the time a character has any real skill at anything in 4e, nonmagical items are practically worthless to them. If a crafter-type character (esp. an Artificer) wants to repair a mundane item, I'd say let them do it, without even a roll1. If there's a broken magical item, fixing it ought to be a quest.2
As Exo Waltz points out, there are a few Martial Practices (DDI categorizes them as rituals) which can be used for crafting/repair:
- Forge Armor: Creates a Magic Armor with no special enchantments, at the normal cost for the appropriate +N Magic Armor. If the enhancement bonus is high enough, the armor can be masterwork.
- Forge Weapon: Creates a Magic Weapon with no special enchantments, at the normal cost for the appropriate +N Magic Weapon. By increasing the cost, the weapon can be silvered.
- Master Artisan: Create mundane items, at the normal cost for the item.
- Temporary Fix: Repair items as with Make Whole at the cost of a healing surge, but the item returns to its damaged state after 24 hours.
- That said, I wouldn't let them repair stuff in the middle of an encounter. Have them repair stuff during a rest or downtime.
- There is the Make Whole ritual, which can repair any item which fits within a 10ft cube, although you must pay 20% of the item's cost to use the ritual.
REPAIR: The Make Whole ritual can permanently repair an item (costing 20% of the item's value), and the Temporary Fix martial practice can temporarily repair an item (costing 1 healing surge).
CREATE MUNDANE: The Master Artisan martial practice can create mundane items (costing the item's value).
CREATE MAGIC: The Enchant Magic Item ritual, Forge Armor martial practice, and Forge Weapon martial practice can create magic items (costing the item's value). Enchant Magic Item may also resize magic armor (for free), or upgrade an existing magic item (costing the difference between the upgraded and original item's value).
CREATE ALCHEMICAL: The Alchemist feat can create alchemical items (costing the item's value).
IMPROVE CRAFTING: Some feats will improve a character's crafting abilities, such as Mark of Making (Enchant/Alchemist as though you're +2 levels), Master Mixer (Alchemist as though you're +3 levels), Creation Mastery (Enchant/Alchemist as though you're +2 levels, cast rituals faster), Dungeon Enchanter (Enchant faster), Pupil of the All-Father (Enchant as though you're +4 levels, 1/day Make Whole for free if cost <100). There are probably others.