How to Value and Authenticate Rare Pokémon Cards on Pokécardex?

[pettyinvolve]

Hello Pokécardex Forum Members,
I am new to collecting Pokémon cards and have recently acquired some cards that I have found to be quite rare, including some holo and promo versions from older sets. I was wondering if there is a tool or guide on Pokécardex to value and authenticate the rarity and condition of cards? Also, are there any members with experience in sending cards for grading who can share the process and notes? I would love to hear some advice from experienced collectors.
Thank you very much!