If you do pull the instrument cluster, look closely at where the two connectors plug into the back of it. The cluster uses a flexible plastic printed circuit, and it's a relatively common failure point, from corrosion or accumulated crud, for breaking (and failing) a circuit where the connector's terminals touch the contacts on the printed circuit.
To clean things up you can use a pencil eraser and alcohol on the cluster side, and emery cloth and alcohol on the connector terminals (or electrical contact cleaner if you want to get fancy). Connector terminals can also be carefully pried up with small pick tool to make better contact, if needed.
You gotta pull the cluster to check or replace the bulbs.
If the cluster is pulled, you might as well go ahead and put all new, good name-brand bulbs in it. And while you're at it, clean the contact points for the bulb sockets using the same routine as cleaning the two main connectors.
I've found that once the cluster is unscrewed from the dash, go down and pull on the speedometer cable where it comes though the floor. Usually you'll get one or a few inches of cable slack from outside, and it'll push the cluster away from dash and give you more room to get your hand behind it to uncouple the speedo cable from the cluster. Feel for the square tab on the cable end; push it in, and the cable should pop loose. Squeeze the skinny ends of the electrical connectors to unlatch the locking tabs.
It's not that bad of a job, once you do it. It can be frustrating if you haven't.
Good luck!