Since SimPE is the easiest way to get your sim into bodyshop, and you don't have it, you will have to package the lot. In neighborhood view, click on the particular lot the sim is in, click info, then click on package lot. Package lot to file on the computer and it will show up in the packaged lot file in your sims 2 folder.
Open the file for the lot containing the sim, and click on family only if you have clean installer. This will only work with the clean installer. Clicking on family only will have check marks in the files that contain your sim. Hopefully the sim hasn't met anyone yet, or their files will be included and you have to shift thru them.
After clicking the files that only contain the sim you want, then click "save as" at the bottom of the clean installer and rename the file. After that you should have a package for your sim. Re-install the package and it will be in bodyshop. It can be tedious. I highly suggest that you install SimPE and follow tutorials on packaging sims in your game. The tutorials are available here and modthesims2.com. Hope that helps.
