Leaking oil sender !!

I found the leak its the oil sending unit, , whats the trick to install new sender , Do i need to remove distributor cap etc.?

Yes, you will have to remove the distributor and there is a specific procedure involved. I highly recommend getting a Haynes repair manual for your truck and reading the section about how to do this job. It's not hard, just have to follow the steps correctly.

I got a nasty oil leak as well haven't thought about the sender at all looks like I have something else to look at to replace!!