NCMountains

I have searched and read many forums regarding this issue. I especially liked 99SC4Runners thread. Just asking for some friendly advice for my situation explained below. Thanks is advance!

I'm a newbie to this forum and to the world of my 3rd gen. 2000 Limited T4R. I have been lurking for a while and finding some valuable info on this site.
Being Labor Day, my local mechanic is closed for the day, but before I take my rig in to see him this week I want to be as educated as possible as to what I may potentially be dealing with here. So here is the situation....
Driving home from the beach yesterday, cruising around ~65-70mph down I40. Out of no where, my dash 4X4 light starts flashing. I panic and start yelling at my kids for what I thought was one of them accidentally hitting something on the shift lever, etc. The weird thing was that the flashing was intermittent. I pulled into a rest area and ran thru the various 4x4 options (4H, 4L) and everything seemed to engage correctly. FYI - this was the first time I have engaged any of the 4x4 options (re: I had not used the 4x4 mode before the flashing started). For the next 2 hours of driving, the flashing light would come and go very randomly.
I have read thru pages of the threads related to this and feel almost overwhelmed. I don't expect anyone to diagnosis my problem thru an online forum, but if anyone had this same exact problem or has suggestions please let me know. BTW, drove 22 miles to work today with no flashing light. Here are a few things I've gathered:
1) Suggest to mechanic that there could be a bad switch/sensor on the front diff and/or the transfer case sensor
2) check vacuum lines
3) FYI - all of the fluids (diff, transfer, etc.) were changed in rig before I purchased it

Thank you in advance and happy to be apart of the 3rd gen herd!