Welcome to the Forum
Firstly, I'd like to say that one issue that makes reading music difficult for some is that they already "know how to play guitar"! IOW, some people can play quite well by ear alone and it's really hard for them to step back and learn to read.
As a result, it seems to them a very slow and tedious process.
If you fall in this camp - even though it does sound like you're ready to bite the bullet - just be aware of this so you don't get frustrated or too hard on yourself - it's a process, and in many ways, a lifelong process.
I would recommend some "graded" music repertoire for guitar. Ideally you'll "learn to read" while you "learn the piece".
Don't cheat and use tab though!
I'd also recommend this:
1. Just pick a short, easy, melody - like a nursery rhyme or folk tune - something you're familiar with - and try to read through it. Do one every night. Since the melody will be familiar, you can "check yourself" - you know, you think you read an E, you play it, and you're like "that doesn't sound right", you can check against your mental memory of the melody. While it's useful reading unfamiliar pieces, it's sometimes harder to check yourself - and I would avoid using tab to check yourself (for pieces that have both a standard notation and tab staff). It may make you "slip" and not focus on the note-reading on the staff.
2. Also, find an App for note reading practice so you can also practice reading notes on the staff away from the guitar. You can then do this on a lunch break or if you commute but don't drive, any time you have a few minutes really.
3. Likewise, there are rhythm Apps out there for the same purpose. Most people focus so much on pitch when they're learning to "read music" that all they're really doing is "learning to read pitch" - not *music*. You need to also be able to read rhythms as well.
4. With that in mind, you can take those short melodies like I mentioned in #1 and play ONLY the pitch content once through, then tap out the rhythm another time through, then play both elements together.
5. There are plenty of pitch reading and rhythmic reading exercises online. Use these to *supplement* working on *real* music. Exercises like those are more often designed (if designed for any real purpose) for practicing sight-reading, which is the ability to read quickly a piece you've never seen before. That's a great skill but if you don't have the basics down yet, those exercises can be useless to you.
6. There are many Method books aimed at beginners. Some of them are available online in PDF form but many are not horribly expensive. Grab a couple, start on page 1, and work your way through them. The classic Mel Bay method book (even though not specifically for classical) comes to mind.
IOW, the more you can do, the more quickly you'll get better. Try to read something at least once a day, or as many times a day as you can - you don't need to spend the entire day doing it, but set aside 15 minutes to read through some melodies, maybe 15 minutes to read through a classical piece, and then maybe 30 minutes to work on a variety of reading exercises (but primarily, music, not exercises).
It may take you 30 minutes to work through Mary Had a Little Lamb at first!
Once you've worked through MHALL, don't play it again! Move on to a new piece. Do this for a week (assuming you're consistent) and go back after a week and try MHALL again and I bet you'll be surprised by how much progress you've made!!!
I"m just using MHALL as an example of course, but you get the idea.