You haven't given enough information about your file for us to help much with question 1.
If it's a text file, use fopen, fgetl or similar and fclose. If it's a binary file, use fopen, fread and fclose.
For question 2., if it's a binary file, fread can read the data as signed integer as is. Use:
out = fread(fid, numvalues, *int16);
If it's a text file, convert your hexadecimal string with:
out = typecast(uint16(base2dec(hexstring, 16)), 'int16');
