I will explain the general rules for Spanish as spoken in Spain, but there's not a single way to pronounce Spanish in Spain: there is substantial regional variation. I'd also caution you to think of Latin American Spanish as having some sort of "lag". All dialects of Spanish have a number of features that are innovative to some degree (and often considered unacceptable for Standard Spanish) while preserving features that historically were more common but now are rare. Spanish was already a very diverse beast before expanding into the Americas. There's little rhyme or reason to it besides to some extent which parts of the Americas were populated by which groups from Spain and when that happened.
Vowels are mostly the standard 5 that you are taught, with exceptionally small allophonic variations that aren't really worth talking about. However, if you opt to adopt to the aspirated syllable-final /s/ pronunciation, you should know that speakers in the South of Spain have a tendency to adjust vowel quality to increase the distinction between, for example, gata [gata] and gatas [gatas](norm) ~ [gatæ(h)](adjusted). Basically /-as/ is pronounced [-æ(h)], /-es/ is [-ɛ(h)], and /os/ is [-ɔ(h)] for these speakers.
For /b/, /d/ and /g/, there is little difference with Latin America. Intervocalically, they soften, with the /d/ even disappearing sometimes in semi-formal speech. A word-final /d/ can be variably pronounced [d] ~ [t] ~ [θ]. In central Spain, [θ] is most common, hence one of the main local magazines is literally entitled Madriz. But in the northeast, that same /d/ will be more like [t]. Elsewhere, it may stay [d] or just disappear entirely. Note that the letter v is always pronounced /b/, identical to b.
The ll in some areas maintains distinction with y, and in others it doesn't. If you wish to maintain the distinction (also common in the Andes), you should pronounce the y very close to the English one. If you don't, aim for something between the English /y/ and /j/ (but closer to the /y/), and just like with native speakers, the actual pronunciation for a given word may end up sounding a bit more like one or the other, but it'll be quite close.
In many parts of Spain —like in some parts of Latin America— an /n/ at the end of an utterance will be [ŋ] instead the [n] that you might expect. This is most common in the North, South, and the Canaries, and not common in Central or Eastern Spain.
The /ks/ from x will be simplified most of the time in front of a consonant to just /s/. Hence texto and testo are identical in pronunciation. This can sometimes even spill over into intervocalic /x/ and result in something like taxi being /tasi/.
The /s/ has a variety of different sounds including [s̺] or [s]. The latter is pronounced like the English S, and the former is like that but with the tongue curled ever so slightly upwards, creating an almost sh like sound. At the end of syllables, it may be aspirated (particularly in the south) potentially resulting in vowel changes (see vowel section). It can even be [x] or [χ] in front of /k/. In front of voiced consonants, it can also voice, such that mesmo sounds like [mezmo] (English z sound).
The ch is generally as in English [t͡ʃ] but in the south can be simply pronounced as [ʃ] (like English sh).
The rr is pronounced as an alveolar trill, and there isn't really any variation on it.
The s/z distinction is the norm, but not universal. There are substantial areas in the South and a few in the northwest that do not distinguish them. In the northwest, it's universally pronounced like s, but in the south, some will pronounce both like s /s/ and others will pronounce both like z /θ/.
The h can be pronounced in some words in a few very small regions. As a result, words like albahaca, while normally being pronounced /al.ba'a.ka/, they will be pronounced /al.ba'ha.ka/. 99.999% of speakers in Spain will never pronounce the h.
The j and the g in combination with e or i tends to be pronounced further back in the both and with more friction than other dialects. Thus we could write it as [x] ~ [χ] instead of [h]. You'll definitely get the feeling you're coughing when pronouncing this correctly for European Spanish.