Yes, play through ME1 all the way. Other wise, the choices you don't make get made for you, and that's no fun at all.
With regards to the Mako, seriously, am I the ONLY PERSON IN THE UNIVERSE that enjoyed it? I thought it was fun! It was at least realistic. The thought that all planets in the galaxy would have Earth-normal gravity is stupid, and the moments with the Thresher Maw were made only that much more tense, scary, and filled with thoughts of OH GOD OH GOD OH GOD THAT GIANT WORM THING IS GOING TO EAT ME when coupled with the fact that I couldn't control my car as easily as the Warthogs in Halo. It also made me feel like even more of a complete badass when I finally killed the thing. *Sigh*. And be honest, was the planet-scanning mechanic AT ALL BETTER than the Mako? I don't care if they made us play riding a toboggan on the ground in ME3 if it means I don't have to go through the god-awful process of resource mining again.