I haven't done an H3.... but I did a Vette Coupe, Camaro Z28... and of course my old Ford ranger. All you need are simple hand tools... and the job is easier usuallyif you have a set of hog ring pliers available at any auto parts place...

I honestly think you will be pissed if you pay someone $400 to do it... especially if you aremechanically inclined.

But... judge for yourself.... here is pretty decently detailed set of instructions for a Mazda...
http://www.worlduph.com/seatmazdainstructions.htm

 

http://www.shearcomfort.com/ Is where i got my seat covers, but i think they have some general installation directions too...

 

The headrests are injected molded foam, so your going to need to get a matching set off of Ebay.

 

Hi,
I also sell the leather seat replacements for the H3.......I've sold many for the Dodge Ram rumble bees and everyone loves them......I have not done an install on the H3 as of yet, but they are very easy to install.....they use all the original installation points....
Be sure if you buy from ebay, that they are leather and not pleather look-a-likes.....