I'm not a plumber either...but I was able to removal of a leaky saddle valve. Mine was for a deceased humidifer on my furnance. Here's what I did:
- shut off off the water
- cut back the pipe with a tubing cutter
- drained the water from the pipe by pulling it down a bit
- put a real valve in (ball cock)
- put a short 12" nipple(dead man) on that
- soldered the thing up (clean w/emory and apply flux before soldering)
- put a cap on the "dead man"
Now when I buy a new humidifer, I can put the saddle on the dead man...if it ever leaks, I shut off the valve, remove the bad saddle, cut out that one inch of pipe and recap it. Done. I could do it about 12 times before it ever became a real issue again.
All told, it took me maybe an hour to do.
I have seen some putty that is *supposed* to seal a pipe - but I have no idea if it will actually hold for any duration of time or if it is just a band-aid.
If you are able to get in there and do the work, or lack the ability/confidence to do the work...call a plumber.
Side note: Do not use duct tape to try and seal it. I was over at my MIL's the other day..turned on the outside faucet and was given an unwelcome shower. Apparently, the pipe had burst at some point (from freezing) and the solution was duct tape. Sure, it held for a few years (judging from the layers of paint on the tape)..but it "blew" at a bad time - fortunately, I was there at the time otherwise who knows how long the thing would have ran for?