The schematic diagram is available on the www.daiwa.com
site. Go the Site index & click on "Parts Diagram". In the search box type "Sweepfire" & select "Spinning" in type of reel. You will get a list of diagram's. Choose the 3550RA & click. You will get the schematic. The method to open is rear drag is very clear in the schematic diagram.
Pl elaborate on the type of problem. I open & service my reels & have repaired a few spinning reels. If a part is broken, you will have to import the part. If you want me to take a try, you will have to ship it to Pune. However, no guarantee & NO charges. Only shipping cost. Other option is to ship it to a Daiwa repair centre.