Everything you want here requires you to have LUA Knowledge...
In order to give the player back the skin they had before they died, you would need to use:
onPlayerWasted then get the player skin using: getElementModel, and store it in a variable or a table, after the player spawns(onPlayerSpawn), use setElementModel and set the player skin back.
Also, for the ammo and guns, you could use the same events, but you would need to loop through every slot and get the guns ammos.