long paranoid / newb question about my S14 body condition...

Isn't there a way to replace every part on an S14 and for cars in general, isn't there a way to cut-out rust and just melt some new metal into it??? i hear muscle car heads talk about that method all the time.

but if its true, then why isn't my paint shop doing it to get rid of the rust spots??? i told them i wanna repaint my body and do the body work on it to last "forever" and do it right... but they are just using filler for the dents and rust... isn't that going to hold moisture and make my car ROT QUICKER??

i want my s14 to be an early hotrod and not just some drift slut that will be in the junkyard or some 16 year old's possession, cheaped out, spray painted black and smoked lights in the next few years...

The thing is i have quite a few "bad spots" on my car...

1) Window & weather strips: My rubber strips above my windows are peeled back with gaps in them... meaning water can come inside... how do i fix them??? what shop can restore them back to how they should be???

Also, the rubber lining at the bottom of my windshield... well... i took off that whole panel one day to clean all the leaves out from the drainage holes in my firewall and now it wont stick in... idno how to fix it... help!

2) Dents/scratches/ Body history: I know front fenders can be replaced... but what about the rest of my car??? how the hell do i get rid of the rust on my roof/ that beam under my door? and how do i get rid of the dents on that beam too?? the beam where u step under the door has a small but deep dent from a pipe that fell onto it and it has rust growing in it now from the metal... how do i properly fix all these things professionally????

I'm also worried if my car was in a MAJOR accident before, and the previous owners just welded it together with another car or hammered out the dents and changed around a few parts... i know its been in a rear end collision and a passenger side front nose collision (or one in the same) i just don't know how bad... how can i professionally tell if my chassis is still straight and CLEAN or if its been covered up? i don't want my frame to be bent AT ALL and i never want to have an accident for peace of mind and have a perfect body... not even fixing a damaged frame is good enough for me, it has to be perfect and never altered... how do i tell that???

3) RUST RUST RUST!!!: I FUCKING HATE RUST! How easy is it to get rid of rust and KEEP IT OFF?? What i don't want to happen is to paint my car only to find out its rusting underneath!!! thats why im getting fiberglass fenders and a hood...

is there Really a way to just "re-forge" new metal into the rust spots to keep my body lasting forever and if so, why isn't any shop i ask acting like they know wtf i'm talking about????