Numrich gun parts
Depending on condition, $100-$150.
On line auctions, gun shops, gun shows, pawn shops, want ad, for sale ad.
50-100 USD
150 miles
depending on the condition any where from 150-400 remember that's depending on the condition usually the most would be 200 but it does range
I believe it was a Marlin model 49. I had one of these myself in the 60's. If you are trying to find replacement parts, then you can use the Marlin parts as is. That is what I did, parts for Marlin are easier to find and sometimes cheaper.
In good condition, with all working parts, around $150.
You might be able to find an SKS in the $150 - $200 price range.
If your Revelation 150 is a tube fed semi-auto .22 rifle, it was likely made for Western Auto by the Marlin Company, and is a Marlin Model 49. Depending on the part you need, you may find it at gunpartscorp website, or check with a gunsmith.
The Revelation Model 150 is a Marlin model 49: See; http://www.e-gunparts.com/productschem.asp?chrMasterModel=082Zz49+RIFLE MARLIN 49 RIFLE Barrel, .22 Cal., 22", Used, Stamped Revelation 150
To find out the age you would need the serial number of the rifle. They were made in the 1950's and 1960's. They generally price for $100 to $150.
Take it to a gun smith.