Is it worth converting a steel frame Trek Roadie to a Cyclocross? I have a Trek Elance 330 from the 80s and love it!  However, I find myself needing something that can handle fire roads (gravel jeep paths) and am wondering if it is worth the effort.   Also, if it would result in an effective ride.  I am fine with the higher center of gravity, won't be doing any rock hopping, and won't be buying a new bike.  Has anyone converted their steel frame?  What experience can you share?  Thanks!  :)
I've done a conversion on an old steel Schwinn, and these look similar. I'm not sure how in-depth you want to go, but at the most basic level you only have to worry about two issues:


Tire clearance
Brake clearance


Tire Clearance
The most popular size of cyclocross tire is 700x32. You may find that a knobby cyclocross tire will fit between your fork, but not clear the bottom bracket or chainstays in the rear triangle or vice versa. If you have a tire clearance issue with the rear triangle I would abandon hope right then. If the rear is fine but the front is tight, you can consider a new fork.

Brake clearance
The brakes on that bike may not have arms that are wide enough or long enough to properly place the pads on the rim without touching the tire. IF that's the case you can check a touring source like Rivendell for brakes with longer, curvy arms.

Note: If the bike came with 27 inch rims, you may have a hard time finding tires and your clearance issues may be even tighter. If that's the case you can look at switching to 700 wheels, but you may find on an older bike that it expects a narrower hub. With a steel frame  you can consider carefully bending the forks.

Is it worth it?
Well - to me it's worth it if you will ride it. Start with the tires - that's the cheapest first step. Move on to brakes and fork only if you have to.