Front Skid Plate Question/Transmission Oil

I just had the Bilstein 5100s installed all the way around and the guy who did it left the skid plates off when I picked it up. I have two plates and nine bolts, can anyone tell me the best way to reinstall them? Also he said I had a front differential leak and needed it rebuilt. I had him hold off until I took a look at it. I washed off all the grease and mud and it looks like it is not leaking at all after 2 days. I know when I have changed my oil it drips from the filter down to the front diff. Is this a possible cause of making it look like it was leaking?

Last question is for those who are familiar with the 5 speed manual transmission. I was going to change out the gear oil but want to make sure I got the right bolts for the drain and fill plug. It looks like the fill plug is halfway up on the drivers side and the drain plug is on the bottom on the passenger side, am I looking at that right? My tacoma is a 2001 TRD Offroad. Thanks in advance.