Cluster Problem and Need Directions for Replacing Oil Pump

I have an Early 87 Pioneer Cherokee.

I have the Idiot cluster... but with Oil, Temp, and Volt Guages....

But I want the RPM tac instead of the Gas

I recently found a 90 Laredo Cluster for sale thats exacly what I want, will it hook right up, or will I have to replace sensors, or senders?

Also looking for directions on replacing my oil pump... Haynes isn't helping me much.

Thanks
Corey