Bushido Helmets stats:
Melee Skill Boost 3
Critical Hit Boost % 3
Health Steal % 2
Dropped by Redeemed for 4000 Challenge Points

My question is: Those 3 basic type of buffs are permanent? I mean during entchanting could be Melee Skill Boost replaced by Distance or Magic level boost?

No, melee is a base status.
Btw, you canot get any kind of "skill" in head gear by enchanting, no mlevel distance or melee.

Bracers have mlevel distance or melee skills addable

basic info:
bluestone bracers:
Defense 4.8
Magic Resistance % 2
Dropped by Villumb

My :
You are looking at bluestone bracers in the Epic tier (attack 0.0, defense 5.4, +3 magic level, 2% magic resistance, 2% experience boost, 2% loot boost). Only a level 150+ player can wield it.