Will I encounter any big issues?: Not likely (assuming the CD is good)
Will i lose any functionality?: You should GAIN functionality with Pro over Home and any dell utilities that shipped with the machine should work fine on Pro as well (not sure why anyone would want those however)
Will it void my warranty?: It should not void your warranty, the worst that would happen if you had a major issue is support might ask you to install the original operating system again.
although that has only happened to me once after all other attempts at a fix failed (I ended up sending the unit to Dell for repair)