New cam and heads for original 273?

So the timing gears crapped out on my 69 Dart 273 at 107,000 original miles two weeks ago. Valves are bent, pushrods bent, cam gear now perfectly round its a mess. I know i could get my heads rebuilt, in fact there's a great machine shop nearby. But maybe this is my opportunity to upgrade! :D

My engine is %100 stock but i was thinking about getting a slightly more aggressive cam and new heads. I have a couple questions...

1. Can someone please explains cams simple for me??!!?? Once people start talking about diration this and lift that with all the different degrees i start getting confused and have relapses of math class

2. Aside from trying to throw some slick new aluminum heads on it, whats my best bet with the heads? Rebuild stock? Rebuild with bigger valves? Will 318 heads fit on the 273

I need all the help i can get :)

TheOriginalDart