Bicycle Mechanics - Shimano 105 shifter

I have 105 shifter/brakes on my road bike. The bike is set up with an 8 speed cassette in the back and dual in the front. My problem is that my left shifter will not "click" when shifting from the small to the large chain ring on the front. It moves the derailleur from left to right, the chain will engage the large chain ring, but if I let go of the shifter, the derailleur falls back to the small chain ring as if the shifter does not engage. Right now, it is being looked at by the fellas at the LBS, but I'm not sure they are very well versed in shifters (I live in a rural setting) so I'm posting here. My question is, first, does this sound like a shifter problem rather than a derailleur problem, and second, if I do have to replace the 105 brakes/shifters, what are some cheaper options. The bike is a crosscheck, I'm not really married to the idea of drop bars, and I'm looking to save a few bucks.

Thanks in advance for any advice.

The problem is not in the derailleur.

Try reducing the cable tension. This may be all it needs.

Try flushing out the insides of the shifter with WD40.

Try adjusting the derailleur and cable. With the chain on the largest cassette cog and smaller chainring detach the cable from the front derailleur.
Set the derailleur's low limit screw so that the inside rail clears the smaller chainring by 2 or 3 mm.
Flip the smaller shift lever several times.
From the derailleur end of the cable pull all of the slack out of the cable.
Reattach the derailleur cable, be careful to route it correctly.
Try shifting to the big ring.
Using the barrel adjuster you may need to add a small amount of tension to the cable.

Al