As a long time 40k player who made the jump to fantasy with 8th edition, I can say that the transition shouldn't be that difficult. This is especially true if you've played older editions of 40k.
Many of the core mechanics are the same. The characteristics are the same (WS/BS/S/T/I/W/A/Ld/etc.), units have a "Move" characteristic (like in older editions of 40k). Morale saves are similar and used in similar situations, and most of the combat systems are exactly the same. (e.g., WS v WS for melee combat, or BS for shooting)
Rules wise, movement is a bit more important in Fantasy than it currently is in 40k. Units have a LoS Arc that determines who/what they can charge or shoot, versus the 360 degree LoS that infantry in 40k have.
If you played with the old Dark Millenium supplement to 40k for psychic powers, then you have some idea what magic in Fantasy is like. Overall, the rules jump is not all that difficult.
Lizards are definitely a solid army. They have good Ld rules to stop them from running, solid infantry, one of the best casters available and are generally a good all-round force to have.
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