These are not difficult jobs, but you need a good set of metric tools, especially hex-bit sockets and a way to get the entire car a couple of feet off the ground.
The entire exhaust will probably need to be replaced from the manifolds back and do not even think about dealer parts. I would warn you that a cheap Mercedes, especially a 107, can become a very expensive car if it has been neglected.
Do a search on Wayward Woman to see my investment in a cheap 380SL.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe