Cluster Question and Directions for Oil Pump Installation... HELP

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

the new cluster should plug right in with no wiring. all jeeps are prewired for everything in the factory including a tach.