I think it's a good idea to keep conversion as simple as possible. In other words, when possible calculate everything as if you were making a new ranger character at your character's level.
1. Hit Points. Use d8s. Full hit points at first level, roll for other levels.
2. Skill points. Figure out how many skill points you'd have if you were creating a new ranger at your ranger's level. Subtract your current skill points from this total (except for skill points from skills that no longer exist). Apply the result however you wish.
3. Animal companions. Apply the new animal companion rules to your current companion.
4. Spells. Use the new spells and spell tables. Ranger spells are Divine, and Divine spells work in mysterious ways.
5. Feats and abilities. This is the biggest potential source of difficulty. To keep it as simple as possible I'd just give your ranger the new feats and abilities of his level (including picking a combat path), and allow the player to re-chose feats for the character.
6. Equipment. If your ranger has magic medium armor I'd let him exchange it for light armor. So, if your ranger had +2 Silent Hide armor I'd let him exchange it for +2 Silent Leather armor, or Studded Leather, or any other Light armor. This exchange would be free, with no cost or refunds from differences in price.
7. Favored Enemy. Keep the current favored enemies, but use the new rules.
-z