Hello, and welcome. It is perfectly normal for your gauge to reach just past the M in NORM before your low speed fan kicks in, then drop back to about between the R & M. This is especially true when traveling slowly in warm weather or in traffic.
As for the stuttering you noticed, this is most likely what many notice after shutting the engine down for a little bit then restarting it. It is widely believed to be either vapor lock or leaky injectors, and somtimes occurs when the engine is restarted warm, especially on warm days. Other than the abnormal idle, this isn't really harmful. Try running some Barryman's fuel cleaner through & see if that doesn't help.
As for the shifting difficulties, your clutch may be starting to wear down. I believe these symptoms are sometimes attributed to the throwout bearing. If the trans doesn't grind when shifting, have the clutch looked at. A bad clutch can lead to bad synchros, which is something you want to avoid. You can also try having the clutch hydralic system flushed & refilled, with either DOT 3 or 4.
Lastly, there are shifter rebuild kits available for the SC. It is likely that one of them would suit your needs. Others can recommend these.
Hope that helps..