Short version: What parts and procedures do I need to replace the Immobilizer antenna in a 1999 V70. Seem like everybody that has this issue just lives with it?

Long version with background:
I am new here. I am a Buick collector, but last Fall a 1999 V70 (no turbo, plain old 5 cyl) fell into my lap. It was on it's way to the junkyard because my neighbor spent over $1000 at a shop (timing belt, water pump, tensioner) and then the shop called and said, it still won't run, so we need another $3000 to take the head off and fix it.
So they offered it to me if I wanted it. A compression check showed no compression. When I removed the front timing covers I noticed that the shop had placed several dabs of white paint on the cam gears?? Seemed odd, but what do I know?? I never touched a DOHC in my life, so I figured maybe there is some multi step process to get it back in time, whatever, I keep wrenching. I figured I'd pull the head and find a bunch of valve heads laying on top of the pistons. Head came off, no damage, nothing bent, looked perfect to me. Nothing touched the tops of these pistons since Belgium in 1999! Since the head was off anyway, I took it to my local machine shop anyway and let them check it and do a valve job. As stated, I am new to Volvos so as I proceeded I took a ton of photos. (more on that soon). I get my head back, buy all the gaskets, thermostat, hoses, etc. and make myself a jig to hold the cams in place for the assembly. Well I get to where the timing belt goes on and I see something I didn't notice before. The little triangles formed by the cam gear bolts are perfectly pointing vertical, one up, one down. So I go look at the photos of how it was before I took it apart. Idiot shop had the exhaust cam about 6 teeth out of time! Had I known what I know now, I am 99% sure this car would have needed no repair at all. Finished my work , turned the key and runs great!
Fast forward 4 months; now I'm getting to kinda like this car. I replaced all the PITA little interior bulbs (really?!?! a soldering iron to replace a light bulb!), fixed a bunch of little things like the gas springs in the tailgate, tie rods, and every little thing I could find. Almost since the first day I have had this no start deal maybe once a week or so. I go to start it and starts dies and then just cranks like no fuel. I noticed that the up arrow, shift light stays lit when this happens. I try it again, starts, runs perfect. This happens for a number of times recently, so I troll here and decide I need a new fuel pump relay. I buy the good brand from FCP, replace it and I still have the same issue. So that brings us up to date. I have been using two different keys; both do the won't start, then try a couple times and all is well. So I now suspect the antenna. I have never had any running issue, once it starts, it runs perfect. So back to the original question - how big is this job? I have seen all kinds of threads where this is happening to others, and I have not seen any thread where somebody actually fixed it. Does everyone just live with this? Is it some huge dealer re-program process? or what's the straight poop? Thanks

Great board, - glad to be here, maybe someday I can help somebody here.

PS I have VADIS and my wife thinks I have enough tools, but I'm sure she's mistaken

 

CX90 does not turn, message immobilizer actived. Look at the manual. The car will not turn , does not make any noise. The year 2007. Driver air bag deployed. the car said start and dont run because the lower control arm was broken, but I have changed but do not start. Some one can Help. seems like a need reprogram keys ?