can I update my late 2008 MacBook running Yosemite 10.10.5 to HighSierra, or am I way too late? Thanks.

According to the following link, High Sierra is only compatible with MacBooks from late 2009 or later: How to download macOS High Sierra - Apple Support

Not too late but out of date. You cannot install Sierra or High Sierra on a laptop as old as yours. The last version of macOS you can install is El Capitan.

Upgrading to El Capitan

To upgrade to El Capitan you must have Snow Leopard 10.6.8, Lion, or later installed. Download El Capitan from the App Store. Sign in using your Apple ID. El Capitan is free. The file is quite large, over 5 GBs, so allow some time to download. It would be preferable to use Ethernet because it is nearly four times faster than wireless.

Macs that can be upgraded to OS X El Capitan

1. iMac (Mid 2007 or newer) - Model Identifier 7,1 or later

2. MacBook (Late 2008 Aluminum, or Early 2009 or newer) - Model Identifier 5,1 or later

3. MacBook Pro (Mid/Late 2007 or newer) - Model Identifier 3,1 or later

4. MacBook Air (Late 2008 or newer) - Model Identifier 2,1 or later

5. Mac mini (Early 2009 or newer) - Model Identifier 3,1 or later

6. Mac Pro (Early 2008 or newer) - Model Identifier 3,1 or later

7. Xserve (Early 2009) - Model Identifier 3,1 or later

To find the model identifier open System Profiler in the Utilities' folder. It's displayed in the panel on the right.

Are my applications compatible? See App Compatibility Table - RoaringApps.