is this process as easy as swapping the bulbs with LED, and adding the correct relay to the fuse block?
As for the side marker
bulbs, with the equivalent socket size/type replacements, yes just install the LED's.
As for "adding the
relay", I believe you are referring to the 'flasher', in which case also yes. You do not need to "add" one, just replace the existing flasher with the same socket type but for LED bulbs. The regular relays do not need to be touched.
As for taillights and turn signals, etc, same as with the side markers - get the same socket size/type in LED bulbs and replace them. The turn signals are the only ones that require any other items to be replaced, that being the 'flasher' due to the lower amp draw of LED's. Which was covered in the second statement about 'relays'.
So to review for all exterior lighting. It's very easy and straightforward, swap bulbs and flasher to LED types. Done.
For interior lighting it is a little different. The '79's fiber optic dash lighting can be done two ways; replace the single bulb that feeds the existing fiber optic system with a LED bulb, or completely replace the fiber optic system by adding individual LED bulbs to each item where the fiber optic reaches. The first approach is easier, assuming the fiber optic system is working (they tend to fall out of place). But both methods require some minor modifications to get a LED bulb to fit. Search for some great tutorials by people like Bob Brown on how to do it. Also there two types of dimmer switches. You will need the one that can control LED's, again look for the tutorials.
The rest of the interior lighting is like the exterior stuff, just swap the bulbs.