Unless the entire query is controllable from the parameter then no you can't morph a select into an insert or update. However, you can likely alter one or more parameters affecting the where clause of the query. Which along with various comment delimiters may allow you to remove restrictions of the where clause or chain your own query along with the select.
1) Simply assemble the HTTP request by hand and send it via netcat or telnet to the appropriate service etc.
2) Fix your syntax (keep in mind semi-colon normally delimits queries, and that you can use various comment constructs to get rid of bit on the original you don't like).
3) Alter the source code of sqlmap.