Good luck on "book value" for the Mercedes. Those cars sell in a big range depending on number of owners, condition, and service history. If by chanve you find one without the hard top, deduct $15-20,000 as that is what it costs to replace the top.
Go to mercedes-benz.ca and click on pre-owned cars and search dealer's inventories nation wide. They're a good source for a R129 SL model.
Keep something in mind when thinking about the 1990-2002 SL cars. These are not inexpensive cars to own or operate. Keeping one in top shape can cost an arm and leg. The engine bay is VERY tight and all repairs require lots of labour charges. The AC systems are not very reliable and, as an example, replacing the evaporator (a common problem) requires close to 40 labour hours.
That said, the M119 DOHC V-8 engine is deadly reliable and will last nearly forever. The rest of the driveline is also bulletproof, if cared for.
Look for:
Soft top operation is EXTREMELY complex. Making one work properly that is not will cost thousands.
The AC/ACC system better be working well, or expect to shell out huge dollars to make it work right.
Check service records closely. MB four-speed automatics thrive on having their fluid and filter changed every 50K-km's. If not, expect a much shorter life from the tranny. Coolant should be flushed and changed every two years, and MB specific coolant MUST be used. These cars have lots of alloy bits and cheap coolant will wreck them. Also, plastic radiators also get wrecked by cheap "green" coolant. A new rad is only about $600, but the labour to swap it is big.
Check that the pop-up roll bar is working properly. Fixing it can be very expensive.
Make sure the central locking system is operating well. Vacuum leaks can take lots of time and effort to track down, and a new vacuum pump is very expensive. The power seats can also be expensive to repair, so check them closely.
Take the car to a Mercedes tech that works on R129's and understands the cars and pay for a very thorough PPI. Also, ANY 1990 car, and especially an SL, will probably need a couple thousand to just bring it up to "new owner" snuff. Build that into your budget.
