I'm not familiar with the Ford Ranger specifically but I'd recommend this:
Get a plastic scraper (perhaps your wife has one) that is used for cleaning (scraping) cooking stones, iron-ware (like an iron skillet), etc. I have one from Pampered Chef that my ex didn't take when her. Works great for these applications.
Something like this:http://www.amazon.com/Nylon-Pan-Scra...3151398&sr=8-1
Put the antenna on the roof of your truck with the wire facing forward, route the wire under the weather stripping. Use the tool mentioned above to lift up the weather stripping and help guide the wire into the gap between glass/weather stripping/body (there always seems to be a slight gap in there). Route the wire all the way around the windshield on the driver's side just to the bottom of the windshield on the corner. Now, you should either be right where you can feed the wire under the hood or somewhere the is likely a gap there were you can get it under the hood and it will be out of sight. We're aiming for the firewall here. Make sure that wherever your route it that it's not going to be pinched by the good or the hinge, etc.
When you get to your firewall you'll see that you have several bundles of wires going through - they're all surrounded by rubber grommets. What I do is to use a new razor blade (X-acto knife or utility knife will do - you want it sharp, though) and pushing the wire bundle at the grommet over as much as possible so it's out of the way of your cutting, make a small slit in the rubber grommet to feed your antenna connector and the rest of your wire through. Be exceptionally careful that you don't cut a wire or the insulation off a wire or cut yourself, for that matter. Now once you have the slit push the antenna connector through - it'll probably take a decent push because it'll be tight (it's only a small slit) and you're working against rubber. Once the connector is through you should be able to feed the rest by having someone on top guiding the wire and keeping it from kinking and someone with their head looking up the back side of the dash pulling the wire through.
At that point it's just a matter of routing the wire behind your dash (watching for all of the moving parts - I usually just cable-tie mine to current wire bundles because they are already out of the way) to to wherever you've put the radio and neatly wrapping up the rest and tying it (cable ties again) behind the dash somewhere.
If it's a Plug-N-Play radio I'd guess that you shouldn't even have to remove any parts of the dash but can probably just route the wire up and around by slightly pulling back on the plastic panels and sticking it behind the panels.
The only car I haven't been able to do that on so far is my Honda Civic. It has two problems that get into my way:
- it doesn't have the normal weather stripping around the windshield
- The firewall is far enough back to where I couldn't reliably reach it and cut a slit (maybe I could have done it from the inside, though, and used fish tape to pull the connector back now that I think of it - anyway, I just mounted it on my trunk..)
If you're worried about screwing it up get some friend to help you.. Surely there is someone you know or have worked with who's installed car stereos before.
I hate to even add this: Do this at your own risk
(it's so idiotic that we all feel compelled to say this now because of lawyers.)