Draft inducer wont shut off

I want to get a programmable t-stat. Something that is easy to program & is reliable, mid range price. Should I get this at homedepot, Lowes, Granigers, or where?? I check the wires there are 5 (w,y,g,r,blue) the blue is not hooked up to the stat. This is the info. on the furnace Lavergne M# NUGI 100DH03, S# L911966722. I might be getting a new furnace in a year or 2. THANKS

This is our first post here, so I appreciate any input. We have a 13 year old Armstrong furnace that has been called a "builders special" to the heating people we have had look at it. We are not the orginal owners (the house is 13 years old). Last week, when the weather started to turn a bit cold at night, we set the furnace. One morning it was rather cold, and when my husband checked the thermostat, it was too cold for what we had set it for. It turned out that it would try to fire up but would not blow. To make a long story short, it turned out to be a dirty sensor. The first person to see it said that we had a cracked heat exchanged. We were shocked and he said we needed a new furnace. So, needless to say, we wanted a 2nd opinion. The 2nd opinion actually opened up the heat exchange and tested it with some spray and some UV light. He said we had a slight seam gap in the exchanger based on that test. He said it was not a dangerous furnace, but to get estimates and replace when we could. Well, we are in a position to be able to replace it now. We have since had a few more estimates, and all have said it is cheap and go ahead and replace. Today though, we had a guy look at the little window in the heat exchange and he said "well, the flame is not waivering, so there is no gap. You have been told wrong". The person that did the spray test is from a VERY reputable HVAC place around here that is highly respected. We have gotten opinions all over the place. Do you have any advice for us? We just don't know what to do. I'd hate to replace a furnace that may go a few more years, but then if it is in need of replacement, we'd like to do it before winter hits (we have a 2 year old and I am pregnant). They also said there is a ton of rust in the HE. Thanks in advance for any advice you may give us.