Before I jumped into that one, I'd ask a bunch of questions and want more detailed photos. I purchased a 2002 about 4 years ago for $11K and have put an additional $10K into it, and still have another couple of thousand to go before she will be a good 3 foot car.
As others have said, the front bumper is going to be much more expensive to touch up than you think. The metal grill bits will need to come from a wrecking yard. Tow hook covers from the dealer are close to $500 each, and the driver side one contains the outside air temperature probe. Aftermarket tow hook covers are a crap shoot. I had one that would have taken major work to make fit, so I got a used on and repainted it (fortunately Krylon Black is a close enough match for something that is not that visible). I also run a black zip tie around the mounting post to make sure they don't fall out when I hit a bump (remember to change them out at least annually as they deteriorate from the sun and UV rays). While you are in that area, are the fender lines all there and properly attached? I've seen those held in place with sheet metal screws and fender washers.
Check the upper console. If that is cracked/damaged you are looking at another $350 or so from OctoClassics for a replacement that has the electronics holders built in. Most other reproductions do not.
It may be the angle of the photo, but the gap between the hood and the front bumper looks excessive.
Ask if the rain sensor works as well as the light sensors for the inside rear view mirror.
I'm not a fan of swapped out radios unless I can see how it was done. I've seen some really poor installations (wiring) that will lead to problems down the road. Ditto for the antenna. Will that radio even support the stock antenna or will you need a fixed length one.
I'm not a fan of the headlights with wipers. The motors tend to go bad and those lights are not as bright as you hope. You really want the Xeon lights, which are part of the SL1/SL2 packeages (run the VIN to see if either of those are on that car).
Oh yes, keys! You want/need two flip keys. Currently they are not available from the dealer (but they may show up at some point again - you just don't know). There are places that can clone them, but you need to send them a working key for them to clone.
I'd be tempted to keep looking, unless you are up for some DIY adventures. If you go drive the car, do some hard acceleration. If you hear a clunk when starting, it probably needs motor and transmission mounts. The selling dealer most likely can't tell you, but ask if the transmission has been serviced. With that mileage it should have been serviced at least once.
And finally, unless you are stuck on a Black car, you might take a look at this listing from one of our forum members --> For Sale 2000 SL500 Very Good Condition 128,700 miles