What a neat car! I had a 68 230 with a manual transmission and it was a really fun toy to have. The 250 has a better engine. I'm pretty sure it has a double row timing chain and a few other advantages. I ended up getting rid of mine after rebuilding it and never being able to get oil pressure, it was a very sad thing.
It sounds like you just need to do a compression check, and give the engine a good going over. If the cylinder compressions are all within about 10% of each other, then go ahead and put in plugs, go over the ignition, set the timing, and with the problem you describe, check the centrifugal advance to ensure that it is working properly.
I assume that this engine has dual Zentih carburetors. One of the members here, I believe it was wilton went through a very long effort getting his Zeniths right. There should be a very long post or two as of about late February or early March. You should read and study the post(s). Wilton had quite a challenge, but hung on and kept working through it. He finally got the car running well, and showed a lot of folks on this forum what his troubleshooting tenacity was made of.
As long as the CV boots are not split open, you probably have no problem to worry about. As long as the joints aren't loose or making any noise, check with the parts shop on this site and see if the boots are available. It will be a good bit of work, but change them, and you won't have to worry about them any more.
Enjoy your new toy,
'84 Euro 240D, 516K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in