Regardless of age we all started somewhere. My cheap Harbor Freight welder didn't cost as much as that linkage from Brewers. Don't use your age as a crutch, use it to your advantage. I.E. you have time! To figure things out. I couldn't afford new. Look on Craigslist swapmeets parts for sale on this forum put an ad in parts needed on this forum I.E. have some patience young grasshopper....
you asked for help and I tried to give budget minded answers, but that usually takes more time. You can always dial up the internet and slapped your credit card down and buy stuff. You're kind of missing the point of the hobby a little bit doing that though. But in the end if you can take a 727 out and replace it with this a833 I'm sure you can figure some stuff out....
If at all possible, do it yourself. But that can be kindof intimidating when you're not even old enough you buy yourself a beer and dont have a welder or other type of fabrication machinery:D hmm, I'll have to think about what else