I have a similar vintage Miyata 710 that I am refurbishing for my son in law to ride. The 710 is a short wheelbase bike suitable for entry level racing or club rides, or event rides. My comments would also apply to the Miyata that you are thinking about.
These are lugged steel bicycles, so they are generally gorgeous bicycles (when in good shape). Some of the component choices by Miyata are a little strange by today's standards, most notably the top tube shifters. I don't know what kind of shifters came with a 1987 1000. If the wheels are original, there is a free wheel instead of a free hub. You can still buy free wheels, but it is unlikely bikshops will have one in stock, and it will have to be ordered. I think Miyata was an early adopter of 700c rims, so you can replace the rear wheel if you have to.
Basically, you have all the issues of buying a used bike. If the wheels are trashed, they wil be expensive to replace. If the drivetrain is trashed, it will be expensive to replace. If the frame is cracked, don't buy it.
There have been a lot of improvements since 1987 for bicycles, but there is nothing wrong with an older bicycle. I ride a 1993 Paramount (short wheelbase, non touring road bike), and it is a prized posession.
If you can get the Miyata for say $100 US, and the bike fits, then by all means buy it. If the seller wants more than $150 US, then I would save my pennys for another new or used bicycle.