1998 Chevy Silverado Question for: Rasmataz

Engine Performance problem
1998 Chevy Silverado V8 Two Wheel Drive Automatic 132K+ miles

This is the first of several questions that I will Prob. Ask of you over time about this truck.
First a little history. This truck started leaking coolant at the quick connect for the heater and has been hot before.
A year ago, it started losing coolant (found it coming out the tail pipe. Used some Bar's Leak (for head gaskets and such) and it stopped using coolant. A day after this long and drawn out deal of the Bar's Leak, engine started idling pretty high (2000-2500 and now 3000). I still drove it a little just had to ride the brake when in a 30mph zone.
Had a fuel pump quit and replaced that.

Now to the meat:
I had read (by you I think)about spraying TB cleaner around the intake to check for leaks. I did that, and the engine sped up. That means there is a leak, correct? It was on both sides from front to back. I figure it burnt up the o-ring looking gasket when it got hot.
I went today and got a complet set of gaskets for the intake (top and bottom).

Im getting 4 codes (btw thanks for everything about code readers, their a great thing to have around) P0300, P0300pendind, P0507 and P0507pending.

Do you think all this trouble (random mis fires and high idle) could be caused by bad gaskets? Or do I need to get the gaskets in place and plain on making other repairs also?
David