I am trying to keep up with all this security lark..

I am getting confused about this keyless access system…* not available on all models it says in the handbook.
So is this model keyless? I mean to say I use the key buttons to lock/ unlock my,new to me, Mk 4 Jazz…
Also , and I quote “ communication between the keyless remote and the vehicle consumes the keyless remotes battery”
“ battery life is about 2 years…”
So my question is,does this apply to my car?..
And if so how do I replace the battery in the key fob? Handbook doesn’t seem to say,unless I just can’t find it?
And where to buy and how much money?
I am worried about this as in 2 years time I could be sitting in the car but the battery is dead and so the car will not start?
Is that correct?
And yes,I am an old bugger
