Brian, you will level up very quickly in MW2 to get to the custom classes (I think it's level 5 for custom classes, and level 10 for customer killstreaks.) Let me know if you need any class suggestions (weapons, perks, killstreak setups, etc.)
As far as prestiging goes, when I hit level 70, I stayed on it for a week because of the AK47 and didn't want to give up my Akimbo 1887's before they nerfed their range. But I missed the level progression, so I prestiged. At first I regretted it, but after I got my custom classes and killstreaks back, it has been smooth sailing.