My first Gunpla, the Quanta, took me about a week. And I was super slow. They're really awesome, and amazingly articulated. Bandai has some genius engineers for their products.
I prefer MG only because they're bigger and have more details, etc. The HG will run you just over a GI Joe figure, but they're very good for beginners. I forgot about RG. Those are good too. MG in a smaller size.
Also, the instructions are not a hindrance. Yes, they're all in Japanese, but the labels and instructions are so well documented with images and numbers that you won't ever need to read except for label numbers and letters.